REESE  LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA. 


0/7  AJ 


STEEET    PAVEMENTS 

AND 

PAVING    MATERIALS. 


A  MANUAL   OF  CITY   PAVEMENTS:    THE 

METHODS  AND   MATERIALS   OF 

THEIR  CONSTRUCTION. 


FOR    THE   USE   OF  STUDENTS,   ENGINEERS, 
AND  CITY  OFFICIA  LS. 


BY 

GEO.   W.   TILLSON,   C.E., 

•  * 

^President  Brooklyn  Engineers'  Club,   Mem.  Am.  Soc.  C.  K.,  Mem.  Am. 

Soc.  Municipal  Improvements,  and  Prin.  Anst.  Engineer, 

Department  of  Highioayt,  Brooklyn,  N.  Y. 


FIRST   THOUSAND. 


NEW   YORK: 

JOHN   WILEY   &   SONS. 

LONDON  :  CHAPMAN  &  HALL,   LIMITED. 

1900. 


Copyright,  1900, 

BY 

GEO.  W.  TILLSON. 


ROBERT   DRUMMOND,   PRINTER,   NEW  YORK. 


PREFACE. 


IN  presenting  this  work  to  the  public  the  author  does  so  in  the 
hope  that  it  will  answer  some  questions  that  have  been  presented 
to  him  during  the  past,  and  whose  solution  was  only  obtained  by 
actual  experience. 

Fifteen  years  ago  there  was  probably  less  literature  extant  upon 
the  subject  of  street  pavements  than  upon  any  other  one  branch  of 
the  engineering  profession.  Such  great  advance  has  been  made  in 
pavement  construction  during  that  period  that  works  of  that  day 
are  practically  useless  at  the  present  time,  except  as  records  of  what 
has  been  done. 

An  active  participation  in  the  construction  of  municipal  pub- 
lic works,  particularly  in  pavements,  during  the  past  twenty  years 
has  seemed  to  justify  the  author  in  producing  this  book  in  order  to 
show  not  only  what  is  being  done  at  the  present  time  in  pavement 
construction,  but  also  the  evolution  of  the  modern  city  street  from 
the  rude  roadways  of  centuries  ago. 

Much  time  has  been  spent  in  historical  research,  and  in  Chap- 
ter I  will  be  found  a  collection  of  facts  that  makes  a  fairly  well- 
connected  history  of  pavements  and  roads. 

It  would  be  useless  to  enumerate  all  the  works  that  have  been 
consulted  in  the  preparation  of  this  volume,  as  they  include  ency- 
clopedias, dictionaries,  scientific  works,  technical  journals,  society 
and  official  reports,  special  reports  of  consular  agents  and  official 
committees,  magazines,  popular  publications,  and  in  fact  all  litera- 
ture that  would  furnish  information  on  the  subject.  Unreliable 
statements  have  either  been  rejected  or  given  for  what  they  were 
worth. 

The  author  is  greatly  indebted  to  consular  agents  and  city  of- 

iii 


IV  PREFACE. 

ficials,  who  have  cheerfully  furnished  him  with  valuable  and  inter- 
esting facts. 

Much  of  the  information  contained  in  the  chapter  on  Stone  has 
been  obtained  from  different  geologies,  and  the  reports  of  the  U.  S. 
and  State  Geological  Surveys.  The  entire  chapter  has  been  revised 
by  Professor  Leslie  A.  Lee  of  Bowdoin  College,  Brunswick,  Me.,  who 
has  thus  placed  the  author  under  great  obligations  to  him. 

The  chapter  on  Asphalt  has  been  prepared  from  the  writings  of 
Clifford  Richardson,  Professor  S.  F.  Peckham,  and  others,  as  well 
as  from  personal  investigations,  trade  publications,  etc. 

Much  of  the  information  relative  to  the  payments  for  pave- 
ments by  street-car  companies  was  obtained  from  a  report  made  to 
the  Massachusetts  Legislature  by  a  committee  appointed  to  investi- 
gate the  relations  between  cities  and  towns  and  street-railway 
companies. 

The  main  idea  of  the  work  has  been  to  have  it  practical,  so  that 
an  engineer  unacquainted  with  the  subject  could  obtain  sufficient 
information  to  prepare  specifications  for,  and  intelligently  supervise 
the  construction  of,  pavements. 

G.  W.  T. 
BROOKLYN,  N.  Y.,  Sept.  1,  1900. 


TABLE  OF  CONTENTS. 


CHAPTER   I. 

PAGE 

THE  HISTOBY  AND  DEVELOPMENT  OF  PAVEMENTS 1 

Introduction — Ancient  Roads — Roman  Roads — Mexican  and  Peruvian 
Roads — French  Roads — Spanish  Roads — Pavements  of  Rome — Paris 
Pavements — Early  London  Pavements — Pompeian  Pavements — First 
Paris  Pavements — Mexican  Pavements — Pavements  of  New  York, 
Boston,  Philadelphia,  Chicago,  San  Francisco,  New  Orleans,  Cleveland, 
St.  Louis,  and  Albany. 

CHAPTER  II. 

STONE.  14 

Formation  of  Earth's  Crust — Mineral  Composition  of  Rocks — Quartz 
— Feldspar — Amphibole — Pyroxene — Mica— Granite — Gneiss — Syenite 
— Porphyry — Diabase — Basalt — Analyses  of  Granite — Annual  Produc- 
tion of  Granite — Analyses  of  Trap-rock — Sand — Sandstone — Hudson 
River  Bluestone — Medina  Sandstone — Potsdam  Sandstone — Berea 
Sandstone  —  Colorado  Sandstone  —  Limestone  —  Marble  —  Bedford 
Oolitic  Limestone— Trenton  Limestone. 

CHAPTER  III. 

ASPHALT 40 

Derivation  of  Word  ' '  Asphalt  " — Early  Use  of  Bitumen— Definition 
of  Bitumen  and  Asphalt — Maltha — Origin  of  Asphalt — Chemistry  of 
Asphalt  and  Bitumen— Methods  of  Analyzing  Asphalt — Trinidad  As- 
phalt— Description  of  Pitch  Lake — Composition  of  Pitch  Lake  Asphalt 
— California  Asphalt— Maltha — Composition  of  Different  California 
Asphalts — European  Asphalts — Theory  of  Formation — Analyses  of 
Rock  Asphalts — Mexican  Asphalt— Bermudez  Asphalt — Kentucky 
Asphalt — Texas  Asphalt — Utah  Asphalt — Indian  Territory  Asphalt — 
Montana  Asphalt— Cuban  Asphalt — Barbadoes  Asphalt — Asphalts  of 
,  Turkey — Egyptian  Asphalt. 

V 


VI  TABLE  OF  CONTENTS. 

CHAPTER   IV. 

PAGE 

BRICK-CLAYS  AND  THE  MANUFACTURE  OF  PAVING-BRICK 80 

Formation  and  Composition  of  Clays — Kaolin — Characteristics  of 
Clay  —  Shales  —  Fire-clays— Definition  of  ' '  Vitrified  "—Early  Clay 
Products — First  Brick-kiln  in  United  States— Production  of  Paving- 
brick — Manufacture  of  Paving-brick — Crushing  the  Clay — Screening 
— Pugging— Moulding — Repressing — Drying — Burning— Changes  of 
Clay  in  Burning — Annealing — Sorting. 

CHAPTER   V. 

CEMENT,  CEMENT  MORTAR,  AND  CONCRETE 96 

Definition  of  Lime  and  Cement— Early  Cements — Portland  and  Nat- 
ural Cements — Fineness  of  Cement — Variation  in  Cement  Tests— Stand- 
ard for  Tests — Cement  Specifications — Requirements  for  Cements — Ce- 
ment Mortar — Effect  of  Salt  Water  in  Cement  Mortar— Effect  of 
Frost  on  Mortar — Concrete — Early  Use  of — Proportions  for  Concrete — 
Mixing — Amount  of  Material  per  Cubic  Yard  of  Concrete — Voids  in 
Broken  Stone — Proper  Consistency  of  Concrete — Relative  Value  of 
Hand-  and  Machine-mixed  Concrete — Concrete-mixers— Manufacture 
and  Consumption  of  Cement  in  United  States. 

CHAPTER  VI. 

THE  THEORY  OF  PAVEMENTS 135 

Value  of  Pavements — Methods  of  Payment — Forms  of  Pavements — 
Paving  Material — Properties  of  a  Pavement — Cheapness — Durability — 
Traffic — Easiness  of  Cleaning — Slipperiness — Maintenance — Favorable- 
ness  to  Travel — Sanitariness — Consideration  of  Different  Pavements — 
Conclusion  as  to  Best  Material — Application  of  Principles  Deduced — 
Annual  Cost  of  Pavements — Pavements  of  Leading  Cities— Openings  in 
Pavements. 

CHAPTER   VII. 

COBBLE  AND  STONE-BLOCK  PAVEMENTS 177 

Roman  Stone  Pavements — Shape  of  Early  Stone  Blocks — Cobble- 
stone  Pavements— Quantity  in  American  Cities — Cost  of  Cobblestone 
Pavements — Size  and  Shape  of  Blocks — Cost  of  Belgian  Pavement — 
Granite  Pavements— Quality  and  Size  of  Blocks — Specification  for 
Blocks  in  Different  Cities — Preparing  Foundation — Laying  Blocks — 
Joint-fillers — Cross-section  of  Pavements — Concrete  Base— Cost  of 
Granite  Pavements— Medina  Sandstone  Pavements — Cross-walks — 
Granite  Pavement  in  Vienna. 


TABLE  OF  CONTENTS.  vil 


CHAPTER    VIII. 

ASPHALT  PAVEMENTS  ...............................................  211 

Early  Asphalt  and  Coal-tar  Pavements  in  United  States  —  Grades  for 
Asphalt  Pavements—  Character  of  Asphalt  for  Pavements  —  Asphaltic 
Cement  —  Penetration  Test  —  Sand  for  Asphalt  Pavements  —  Wearing 
Surface  —  Binder  —  ^Foundation  —  Method  of  Laving  —  Cracks  in  Pave- 
ment —  Action  of  Illuminating  Gas  on  Asphalt—  Condition  of  Pave- 
ment at  End  of  Guaranty  —  Rock  Asphalt  Pavements  —  Asphalt  Pave- 
ments in  London—  Repairs  and  Maintenance  —  Cost  of,  in  Different 
Cities  —  Noiseless  Manhole-covers  —  Cost  of  Asphalt  Pavements  — 
Asphalt  on  Bridges—  American  Asphalt  in  Europe—  Asphaltina— 
Asphalt-block  Pavements. 

CHAPTER    IX. 

BIIICK  PAVEMENTS  ...................................................  2C8 

Early  Brick  Pavements—  Requirements  of  Paving-brick—  Abrasion 
Test  —  Absorption  Test  —  Cross-breaking  Test—  Crushing  Test  —  Hard- 
ness and  Specific  Gravity  —  Application  of  Results  of  Tests—  Size  and 
Form  of  Bricks  —  Foundation  for  Brick  Pavements  —  Joint-filling  — 
Rumbling  —  Laying  the  Brick  —  Requirements  of  Different  Specifi- 
cations —  Amount  of  Brick  Pavement  in  United  States  —  Cost  of  Brick 
Pavements  in  Different  Cities  —  Amount  of  Material  per  Square 
Yard  of  Brick  Pavement  —  Estimated  Cost  of  a  Brick  Pavement. 


CHAPTER    X. 

WOOD   PAVEMENTS  ..........  ........................................  293 

Early  Wood  Pavements  —  London  Pavements—  Australian  Wood  in 
London  —  Specifications  for  London  Pavements  —  Wood  Pavement  in 
Ipswich,  Glasgow,  Dublin,  Paris,  Montreal,  and  Quebec  —  Early  Wood 
Pavements  of  the  United  States  —  Wood  Pavements  in  Washington, 
St.  Louis,  and  Brooklyn  —  Cedar-block  Pavements  —  Chicago  Specifi- 
cations —  San  Antonio  Wood  Pavements  —  Redwood  Pavements  —  Des 
Moines  Pavements  —  Specifications  for  Des  Moines  Pavements  —  Aus- 
tralian Pavements  —  Chemical  Treatment  for  Wood—  Early  Methods  — 
Kyanizing  —  Burnettizing  —  Creosoting  Zinc  Process. 


CHAPTER   XI. 

BHOKEN-STONE  PAVEMENTS  ....................  .  ......................  329 

First  Broken-stone  Pavement  —  Telford  —  Macadam  —  Merits  of  Mac- 
adam and  Telford  —  Construction  of  broken-stone  pavement  —  Founda- 
tion —  Wearing  Surface  —  Binding  —  Rolling  —  Quantity  of  Stone  Re- 


viii  TABLE  OF  CONTENTS. 


quired— Crown — Cementing  Properties  of.Stone — Sprinkling — Specific- 
ations of  Different  Cities — Macadam  Roads — How  Built — New  Jersey 
Roads — Construction  of'Macadam  Roads — Drainage— Width — Character 
of  Stone — Massachusetts  Roads — Abrasion  Tests  for  Stone— Cost  of 
Macadam  Roads — Specifications  of  Different  States — Maintenance  of 
Streets  and  Roads— Ruts— Sprinkling— Width  of  Tires. 

CHAPTER  XII. 

PLANS  AND  SPECIFICATIONS.  . .   376 

Object  of  Plans  and  Specifications— Prepared  by  Experts — Should 
be  concise — Should  be  Plain — Alternative  Bids — Instructions  to  Bid- 
ders— Certified  Checks  to  Accompany  Bids — Bond — Guarantees— Un- 
balanced Bids — Sample  Specifications — General  Requirements — Re- 
quirements for  Asphalt,  Granite,  Medina  Sandstone,  Brick,  and  As- 
phalt-block Pavements  ; 

CHAPTER   XIII. 

THE  CONSTRUCTION  OF  STREET-CAR  TRACKS  IN  PAVED  STREETS 421 

Early  Construction — Amount  of  Pavement  Maintained  by  Railway 
Companies — Location  of  Tracks — Forms  of  Old  Rails — Forms  of 
Modern  Rails — Recent  Construction  in  Different  Cities — Life  of  Rails — 
Rail-joints — Recommended  Forms  of  Construction — Mileage  of  Street 
Railways  in  American  and  European  Cities. 

CHAPTER   XIV. 

WIDTH  OF  STREETS  AND  ROADWAYS,  CURBS,  SIDEWALKS,  ETC 459 

Width  of  Streets — Width  between  Curbs — Location  of  Sidewalks — 
Curbing — Specifications  for  Dressing  in  Different  Cities — Foundation 
— Concrete  Curb  and  Gutter — Estimated  Cost — Sidewalks,  Stone, 
Brick,  and  Cement — Specifications  for  Sidewalks  in  Different  Cities — 
Gutters — Street  Grades — How  Established  and  Recorded. 


CHAPTER   XV. 

ASPHALT  PLANTS 487 

Capacity  of  Plant — Location — Work  of  Plant — Asphaltic  Cement — 
Stone  Dust— Mixing— Cost— Portable  Plants. 


LIST  OF  TABLES. 


TABLE  NO.  PAGE 

1.  Analysis  of  trap-rock  from  New  Jersey 27 

2.  Crushing  strength  of  different  granites 27 

3.  Crushing  strength  of  Colorado  sandstone 34 

4.  Analysis  of  Bedford  limestones 87 

5.  Analysis  of  Trenton  limestones 38 

6.  Analysis  of  limestones  and  resulting  limes 38 

7.  Analysis  of  different  limestones 39 

8.  Analysis  of  different  asphalts 54 

9.  Analysis  of  Trinidad  asphalt 60 

10.  Analysis  of  rock  asphalts 68 

11.  Analysis  of  Mexican  asphalt 69 

12.  Mechanical  analysis  of  porphyry 86 

13.  Chemical  analysis  of  porphyry 86 

14.  Analysis  of  Portland  cements 99 

15.  Analysis  of  natural  cements 100 

16.  Requirements  for  fineness  of  Portland  cements 101 

17.  Strength  of  cements  of  different  fineness 102 

18.  Strength  of  ordinary  and  finely  ground  Portland  cement 102 

19.  Strength  of  coarse  and  fine  Rosendale  cement 102 

20.  Strength  of  same  cement  from  different  laboratories 103 

21.  Showing  importance  of  sand  tests  for  cement 104 

22.  Strength  of  cement  with  long-  and  short-time  tests 105 

23.  Strength  of  cement  with  long-time  sand  and  neat  tests 106 

124.  Requirements  of  tensile  strength  for  cements 107 

25,  26.   Showing  material  required  for  one  cubic  yard  of  mortar 110 

27.  Showing  strength  of  mortar  when  immersed  in  salt  water Ill 

28.  Showing  strength  of  mortar  when  immersed  in  and  mixed  with  salt 

and  fresh  water 112 

29.  Showing  strength  of  Portland-cement  mortar  when  immersed  in  and 

mixed  with  salt  and  fresh  water 112 

30.  Showing  strength  of  mortar  when  mixed  with  salt  water 114 

31-33.  Showing  effect  of  freezing  and  subsequent  thawing  on  mortar.  114,  116 

34.  Showing  effect  of  freezing  and  subsequent  thawing  on  concrete  cubes  117 

ix 


x  LIST  OF  TABLES. 

TABLE    NO.  PAGE 

35.  Showing  strength  of  mortar  after  second  mixing 118 

36.  Showing  strength  of  briquettes  made  at  different  times  after  the  mix- 

ing of  the  mortar 119 

37.  Showing  volume  of  concrete  from  certain  mixtures 12i> 

38.  Showing  voids  in  stone,  gravel,  and  mixtures  of  both 121 

39.  Showing  voids  in  certain  sands,  stone,  gravel,  etc . .  124 

40.  41.  Analysis  of  proposed  material  for  Portland  cement 133 

42.  Showing  imports  and  home  products  of  Portland  cement Hi3 

43.  Showing  product  and  consumption  of  American  cement 134 

44.  Showing  methods  of  paying  for  street  pavements 138 

45.  Showing  average  life  of  pavements  in  Europe 156- 

46.  Showing  result  of  traction  experiments  at  Atlantic  Exposition 157 

47.  Showing  tractive  force  required  to  draw  one  ton  on  different  streets 

according  to  Prof.  Haupt 1  oK 

48.  Showing  effect  of  size  of  wheels  and  width  of  tire  on  tractive  force. . .  158 

49.  Showing  tractive  force  per  ton  according  to  London  experiments 159 

50.  Showing  tractive  force  per  ton  according  to  different  authorities 159 

51.  Showing  accidents  to  horses  on  London  streets 161 

52.  Showing  accidents  to  horses  on  different  London  pavements 161 

53.  Showing  accidents  to   horses  on  different  London  pavements  under 

different  conditions 162 

54.  Showing  relative  value  of  different  paving  materials 167 

55.  Showing  comparative  costs  of  different  pavements « 172 

56.  Showing  increase  of  pavement  mileage  in  different  American  cities. . .  173 

57.  Showing  sizes  of  granite  blocks  used  in  American  and  European  cities.  191 

58.  Showing  sizes  of  stone  blocks  used  in  European  cities 192 

59.  Showing  crowns  for  street  pavements *. 202 

60.  Showing  methods  of  laying  out  cross-section  of  pavement.' 218 

61.  Showing  sizes  of  certain  sands, 226 

62.  Showing  sizes  of  sands  used  in  different  pavements 227 

63.  Showing  cost  per  yard  of  repairs  to  asphalt  pavements  in  different 

cities 246 

64.  Showing  cost  per  yard  for  each  year  after  expiration  of  guarantee  in 

different  cities 247 

65.  Showing  analysis  of  different  bricks 260 

66.  Showing  loss  by  abrasion  to  bricks  of  different  degrees  of  hardness. . .  266 

67.  Showing  water  evaporated  from  different  bricks 271 

68.  Showing  water  absorbed  by  different  bricks 271 

69.  Showing  results  of  different  tests  upon  different  bricks 275 

70.  Showing  condition  of  hard-wood  pavements  in  London    298 

71.  Showing  mileage  of  street-car  tracks  in  American  and  European  cities.  458 

72.  73.   Showing  analyses  of  different  asphalts 495,  496. 


LIST  OF  ILLUSTRATIONS. 


FIGURE  PAGE 

1.  Possible  formation  of  rock  asphalt 67 

2.  Machine  for  mixing  concrete 127 

3.  Plan  of  old  Roman  road 178 

4.  Cross-section  of  old  Roman  road 178 

5.  Cross-section  of  old  Roman  road .    178 

6.  Plan  of  pavement,  Catania,  Italy 179 

7.  Cross-section  of  a  cobblestone  pavement. 183 

8.  Cross-section  of  a  Belgian  block  pavement 186 

9.  Plan  of  granite  intersection,  old  method 193 

10.  Plan  of  granite  intersection,  improved  method 194 

11.  Plan  of  granite  intersection,  modern  method 195 

12.  Cross-section  of  granite  pavement  on  concrete  base 199 

13.  Example  of  steep  grade  on  asphalt-paved  street  in  Pitteburg 217 

14.  Cross-section  of  asphalt  pavement 235 

15.  Showing  plan  and  section  of  noiseless  manhole-cover 249 

16.  Showing  expansion-joint  in  asphalt  pavement  on  Denver  viaduct 252 

17.  Cross-section  of  a  brick  pavement  284 

18.  Cross-section  of  a  broken-stone  pavement 347 

19.  Early  form  of  street-car  rail 430 

20.  Same  type  used  on  curves 430 

21.  Modified  form  of  Fig.  19 431 

22.  Original  grooved  rail 431 

Centre- bearing  rail 481 

Side-bearing  rail  with  renewable  head 432 

'  25.  Grooved  rail  with  renewable  head 433 

26.  Centre-bearing  girder  rail 433 

27.  Side-bearing  rail 434 

28.  The  Trilby  rail 435 

29.  Modified  form  of  Trilby  rail 435 

30.  West  End  rail,  Boston 436 

481.  Boston  subway  rail. 437 

32.  Ordinary  T  rail 437 

33.  Improved  track-construction  in  Buffalo 438 

xi 


Xii  LIST  OF  ILLUSTRATIONS. 

FIGURE  PAGE 

34.  Another  form  of  track-construction  in  Buffalo 439 

35.  Tie-construction  of  track,  Department  of  Highways,  Brooklyn 441 

36.  Concrete-beam  construction,  Department  of  Highways,  Brooklyn 441 

37.  Toronto  track-construction 441 

38.  Sioux  City  track-construction 441 

39.  Third  Avenue  Railway  construction,  New  York 443 

40.  Detroit  railway  construction ...  445 

41.  Cincinnati  railway  construction 445 

42.  Rochester  iron-tie  construction 446 

43.  Rochester  concrete-beam  construction 447 

44.  Clamp  used  in  Rochester  construction 447 

45.  Yonkers  construction 448 

46.  Minneapolis  constructiou 448 

47.  Track-construction  recommended  in  granite  pavement 453 

48.  Track-construction  recommended  in  asphalt  pavement 453 

49.  Track- construction  recommended  in  brick  pavement 455 

50.  Method  of  making  grooved  rail  in  old  track-construction 457 

51.  Curb  set  in  concrete,  asphalt  pavement 466 

52.  Cy  rb  set  in  concrete,  granite  pavement 467 

53    Section  of  concrete  curb 470 

54.  Plan  of  stone  sidewalk 476 

55.  Plan  of  brick  sidewalk 477 

56.  Another  plan  of  brick  sidewalk ,  477 

57.  Herringbone  plan  of  brick  sidewalk 477 

58.  Section  of  cobblestone  gutter 481 

59.  Section  of  cement-concrete  gutter. 481 

60.  Diagram  of  grades  at  a  street-intersection 485 


STREET   PAVEMENTS    AND 
PAYING  MATERIALS. 


CHAPTER  I. 

THE  HISTORY  AND  DEVELOPMENT  OF  PAVEMENTS. 

PRIMEVAL  man  had  no  pavements  nor  any  use  for  them.  His 
wants  were  few  and  easily  satisfied.  He  knew  of  nothing  outside  of 
his  own  range  of  vision.  Knowing  but  little,  his  desires  were  few 
and  in  almost  every  instance  could  be  satisfied  by  the  fruits  of  the 
soil  or  the  results  of  the  chase. 

But  this  could  not  continue;  as  the  race  increased  and  scattered 
over  the  then  known  world  the  different  divisions  settled  down  into 
communities  or  became  nomadic  tribes.  Different  localities  pro- 
duced different  articles,  and  in  their  wanderings  and  communica- 
tions with  each  other  they  became  acquainted  with  their  different 
products,  and  the  spirit  of  interchange  and  commerce  sprung  up 
among  them.  Feelings  of  rivalry  arose,  producing  wars,  and  there 
is  no  doubt  that  the  commercial  and  warlike  interests  were  most 
powerful  in  promoting  exchanges  between  tribes  and  later  between 
nations. 

At  first  tracks  were  established  across  the  country,  but  as  time 
went  on  these  tracks  grew  to  be  paths,  and  the  paths  roads,  and  the 
roads  developed  into  our  modern  highways,  paved  streets,  and  mag- 
nificent system  of  railroads.  All  of  this,  however,  consumed  a  vast 
amount  of  time,  and  many  centuries  elapsed  after  the  building  of 
the  first  road  before  much  similar  work  was  undertaken  or  the 
modern  boulevard  completed.  While  war-chariots  are  mentioned  in 


2  STREET  PA  YEMENIS  AND  PAVING  MATERIALS. 

history  as  existing  at  as  early  a  period  as  war  itself,  commercial 
commodities  were  transported  in  ancient  times  almost  entirely 
on  beasts  of  burden,.  Hence  the  slow  growth  for  a  long  time  of  the 
demand  for  roads. 

All  records  of  work  done  in  the  early  life  of  the  human  race 
are  indefinite,  and  much  that  ought  to  be  history  and  founded  upon 
fact  is  only  conjecture. 

It  is  said  that  a  little  to  the  east  of  the  Great  Pyramid  remains 
of  a  stone  causeway  a  mile  long  have  been  discovered.  This  is  sup- 
posed to  be  a  portion  of  a  road  built  by  Pharaoh  for  the  purpose  of 
conveying  stone  or  other  material  across  the  sand  for  the  construc- 
tion of  the  pyramid.  As  this  pyramid  is  generally  considered  to 
have  been  built  in  the  fourth  dynasty,  or  about  4000  B.C.,  it  is 
undoubtedly,  if  authentic,  the  oldest  road  on  record. 

Another  ancient  boulevard  is  mentioned  by  historians  which 
must  have  been  built  soon  after,  as  these  times  are  now  considered. 
The  city  of  Memphis  is.  said  to  have  been  connected  with  the 
pyramids  by  a  broad  roadway,  two  leagues  long,  having  a  paved 
and  well-kept  driveway  lined  on  both  sides  with  temples,  mau- 
soleums, porticoes,  monuments,  statues,  etc.  In  fact,  according 
to  descriptions  it  must  have  been  the  modern  boulevard  with  all 
the  accessories  that  the  times  and  unlimited  wealth  would  allow. 

The  Carthaginians,  however,  are  generally  given  the  credit  of 
"being  the  first  people  to  construct  and  maintain  a  general  system 
of  roads.  This  African  city  had  sprung  up  about  600  B.C.  and  by 
its  growth  and  enterprise  became  a  rival  of  the  Roman  Empire 
across  the  Mediterranean.  Rome  endured  this  rivalry  for  a  time, 
but  at  last  she  issued  that  famous  edict,  Carthago  delenda  est,  which 
resulted  in  the  invasion  of  Africa  and  the  destruction  of  Carthage 
B.C.  146. 

The  Romans  without  doubt  appreciated  the  benefit  of  improved 
highways  for  the  rapid  mobilization  of  troops,  for  they  immediately 
took  up  the  practice  of  the  Carthaginians,  and  road-building  was 
always  one  of  the  features  of  their  subsequent  conquests.  It  is 
claimed  that  in  Great  Britain  alone  they  constructed  2500  miles  of 
roads. 

The  Appian  Way  was  built  by  Appius  Claudius  about  300  B.C., 
and  the  Flaminian  Way  some  years  later.  These  roads  were  prac- 


THK  HISlOllY  AM>  DEVELOPMENT  OF  PAVEMENTS.         3 

tically  examples  of  solid  masonry  laid  in  cement  mortar  and  some- 
times several  feet  thick. 

A  traveller  in  one  case  reports  having  crawled  entirely  across 
a  road  under  the  pavement  where  the  earth  had  been  washed  away 
and  the  masonry  had  been  self-supporting.  Such  roads  lasted  a 
long  time.  The  Appian  Way  was  said  to  have  been  in  good  repair 
eight  hundred  years  after  it  was  built.  But  it  must  be  remem- 
bered that  the  traffic  it  sustained  was  of  such  a  nature  and  amount 
as  to  produce  a  very  slight  abrasion  on  the  roadway.  The  stone 
used  was  irregular  in  size  and  shape,  but  laid  in  such  a  manner 
as  to  make  a  solid  roadbed  impervious  to  water. 

Prof.  John  Beekman  of  the  University  of  Gottingen  states  in 
his  "History  of  Inventions  and  Discoveries"  that  the  streets  of 
Thebes  were  regularly  cleaned,  and  thatjhe  Talmud  says  the  streets 
of  Jerusalem  were  swept  every  day,  and  accordingly  concludes  that 
they  must  have  been  paved. 

A  consular  report  from  Palestine  states  that  the  pavements  of 
Jerusalem  laid  by  the  Romans  over  two  thousand  years  ago  are 
still  in  fair  preservation,  but  adds:  "  They  are  indeed  hidden  from 
sight,  and  are  many  feet  beneath  the  rubbish  of  the  city."  It  is 
easy  to  understand  how  a  stone  pavement  might  last  centuries 
under  such  conditions. 

Mexico  and  Peru,  although  not  countries  where  much  transpor- 
tation was  ever  carried  on  by  vehicles,  built  in  ancient  times  many 
foot-roads  of  great  excellence;  those  of  Peru  alone  extended  for 
more  than  a  thousand  leagues. 

In  the  special  consular  reports  it  is  stated  that  more  than  one 
thousand  years  before  Columbus  discovered  the  New  World,  the 
province  and  fclso  the  city  of  Genoa  boasted  of  fine  roads  and 
streets. 

In  France  all  travelling  was  done  on  horseback  until  the  latter 
part  of  the  sixteenth  century.  In  1508  Louis  XII.  appointed  offi- 
cers to  inspect  and  report  upon  the  condition  of  all  roads;  to  repair 
those  under  the  care  of  the  king,  and  to  enforce  the  repair  of  the 
others  by  the  proper  authorities.  Other  rulers  followed  his  ex- 
ample, but  little  good  was  accomplished,  as  these  officers  were 
often  appointed  and  almost  immediately  discharged  so  as  to  create 
vacancies  which  might  be  filled  upon  the  payment  of  a  certain  fee, 


4  STREET  PAVEMENTS  AND   PAVING  MATERIALS. 

thereby  creating  a  considerable  revenue  by  the  sale  of  appoint- 
ments. This  fact  would  seem  to  show  that  corruption  existed  in 
the  carrying  out  of  public  work  in  ancient  as  well  as  in  modern 
times. 

In  the  latter  part  of  the  sixteenth  century  Henry  IV.  appointed 
a  "  Great  Waywarden  of  France."  This  is  probably  the  earliest 
record  of  the  appointment  of  a  public  official  with  a  specified  title 
to  have  systematic  supervision  over  the  public  roads. 

These  different  actions,  however,  do  not  seem  to  have  accom- 
plished much,  as  it  is  recorded  that  as  late  as  1789  the  country  roa'ds 
of  France  were  generally  in  a  state  of  nature  or  worse. 

It  is,  however,  stated  that  in  1556  a  stone  road  was  built  from 
Paris  to  Orleans,  the  portion  improved  being  15  feet,  although  the 
entire  width  was  54  feet. 

The  first  highway  constructed  in  Sp'ain,  after  the  Roman 
regime,  was  built  by  Fernando  VI.  in  1749  from  Santander  to 
Reinoso,  the  labor  being  performed  by  soldiers.  In  1761  regula- 
tions were  made  for  the  classification,  construction,  and  repair  of 
highways  in  general,  but  no  definite  results  were  obtained.  In  1794 
the  matter  was  delegated  to  a  special  bureau  of  the  government, 
but  with  no  better  success.  And  it  was  not  till  1834,  when  an 
engineering  school  was  established,  graduating  its  first  class  in  1839, 
that  any  real  good  was  accomplished.  From  that  time  roads  were 
built  according  to  the  condition  of  the  public  treasury. 

The  first  Highway  Act  for  the  improvement  of  roads  in  Eng- 
land was  passed  in  1555. 

The  above  facts  relate  to  roads  rather  than  pavements  proper, 
and  it  is  interesting  to  note  to  what  size  European  cities  grew 
before  any  particular  attention  was  given  to  street  pavements,  and 
how  many  years  it  required  to  arrive  at  any  satisfactory  results. 
Alexander  Dumas  said  after  a  visit  to  Russia,  in  answer  to  a 
question  as  to  how  he  found  the  streets  and  roads,  that  he  had 
scarcely  seen  any,  inasmuch  as  during  the  winter  season  they  were 
covered  with  snow,  and  during  the  summer  they  were  in  process  of 
repair. 

The  streets  of  Rome  were  paved  in  the  fourth  and  fifth  cen- 
turies after  the  founding  of  the  city. 

The  first  pavements  in  Paris  were  laid  during  the  reign  of 


THE  HISTORY  AND  DEVELOPMENT  OF  PAVEMENTS.        5 

Philip  Augustus  about  1184,  the  square  of  the  Chatelet  and  the 
streets  of  St.  Antoine,  St.  Jacques,  St.  Honore,  and  St.  Denis  being 
the  first  improved.  The  population  of  Paris  at  that  time  must 
have  been  little  less  than  200,000. 

Cordova,  Spain,  although  a  small  place,  is  said  to  have  had 
paved  street's  in  850. 

The  Strand,  London,  was  ordered  paved  by  act  of  Parliament  in 
the  fourteenth  century,  and  streets  outside  of  the  city  in  the 
sixteenth,  although  it  is  said  that  the  first  regular  pavements  were 
laid  in  1533,  when  the  city  had  a  population  of  150,000.  Holborn 
had  some  pavements  in  1417.  Square  granite  blocks  were  intro- 
duced by  acts  of  Parliament  for  Westminster  in  1761,  and  for 
London  generally  in  1766. 

When  the  Forum  Trajanum  was  cleaned  by  the  French  in  1813, 
the  old  Roman  pavements  were  found  on  an  average  of  12  feet 
below  the  then  surface.  The  stones  in  these  old  pavements  were 
polyangular  in  shape,  containing  from  4  to  5  square  feet  and  12 
to  14  inches  deep,  laid  with  close  joints.  More  modern  blocks-  in 
Rome  were  about  2  cubes  long,  and  on  being  set  up  endwise  had 
an  area  of  10  square  inches.  This  would  give  a  block  about  7 
inches  long,  3£  inches  deep,  and  3£  inches  wide.  They  were  set 
on  12  inches  of  cement  concrete. 

A  recent  novelist,  speaking  of  London  in  1516,  says:  "  There 
were  great  mud-holes  where  one  sank  ankle-deep,  for  no  one  paved 
their  streets  at  that  time;  strangely  enough  preferring  to  pay  the 
sixpence  fine  per  square  yard  for  leaving  it  undone."  How  often 
this  fine  was  imposed  was  not  stated. 

Speaking  of  London  in  1685,  Lord  Macaulay  says:  "  The  pave- 
ment was  detestable;  all  foreigners  cried  shame  upon  it.  The 
drainage  was  so  bad  that  in  rainy  weather  the  gutters  soon  became 
torrents." 

Walter  Besant  in  his  "  History  of  London  "  states  that  in  the 
Elizabethan  period  carts  only  were  allowed  on  the  street,  and  their 
number  was  restricted  to  420.  Merchandise  was  carried  on  pack- 
horses.  Also:  "In  the  streets  the  roads  were  paved  with  round 
pebbles — they  were  cobbled;  the  footway  was  protected  by  posts 
placed  at  intervals;  the  paving-stones,  which  only  existed  in  tHe 
principal  streets,  before  1766  were  small  and  badly  laid;  after  a 


6  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

shower  they  splashed  up  mud  and  water  when  one  stepped  upon 
them/3 

In  a  pamphlet  written  by  a  Colonel  Macirone  of  London  in 
1826,  when  the  city  had  a  population  of  1,400,000,  the  author  says: 
"  Florence,  Sienna,,  Milan,  and  other  Italian  cities  have  pavements 
with  especially  prepared  wheel-tracks.  These  tracks  are  three  feet 
in  width,  made  of  large  and  particularly  well-laid  stones.  They 
are  about  four  feet  apart,  and  the  space  between  paved  with  smaller 
stones."  He  further  states  that  these  pavements,  as  well  as  those 
of  Borne  last  mentioned,  are  the  best  that  he  has  ever  seen,  but 
that  they  would  be  too  expensive  for  London.  Also :  "  There  is 
no  species  of  pavement  that  I  have  ever  seen  or  heard  of  to  the 
application  of  which  tfl  the  streets  of  London  there  would  not 
be  many  and  great  objections.  .  .  .  However  true  it  may  be  that 
an  observant  traveller  cannot  fail  of  being  struck  with  admiration 
at  the  excellence  of  the  turnpikes  and  other  roads  throughout  this 
country,  he  must  at  the  same  time  be  very  much  surprised  at  the 
badness  of  the  carriage-pavements,  even  of  the  principal  streets  of 
this  metropolis." 

These  were  the  observations  of  an  engineer  who  had  travelled 
and  examined  the  European  pavements  of  that  time,  and  they  ought 
to  express  fairly  their  condition. 

This  was  about  the  time  of  Macadam  and  Telford,  and  soon 
after  this  considerable  broken-stone  pavements  were  laid  in  Lon- 
don. 

A  pavement  consisting  of  broad,  smooth,  well- jointed  blocks  of 
granite  for  wheel-tracks,  with  pitching  between  for  horses,  was 
laid  in  Commercial  Koad,  London,  in  1825. 

In  1839  there  were  1100  square  yards  of  wood  pavement  in 
London,  which  in  1842  had  increased  to  60,000,  when,  according  to 
a  statement  made  in  the  City  Council  by  an  alderman  during  a 
controversy  as  to  the  relative  merits  of  wood  and  stone  pavements, 
there  were  600,000  square  yards  of  the  latter,  probably  nearly  if 
not  all  macadam.  These  two  items  without  doubt  represented  the 
total  amount  of  pavements  in  a  city  of  nearly  2,000,000  people. 

In  1825  Telford  recommended  the  use  of  stone  blocks  4J  to7| 
inches  in  size  for  street  use;  and  3x9  inches  granite  sets  were 
laid  on  Blackfriars  Bridge  with  mortar  joints  in  1840.  This  was 
probably  the  first  attempt  at  a  modern  stone  pavement.  Eock 


TEE  HISTORY  AND  DEVELOPMENT  OF  PAVEMENTS.         T 

asphalt  was  laid  in  London  on  Threadneedle  Street  in  1869,  and 
in  1873  there  were  60,802  square  yards  or  4.25  miles  of  this  pave- 
ment, and  12,238  square  yards  of  wood,  in  the  city.  This  would 
indicate  that  wood,  as  first  laid,  was  discontinued,  and  was  not 
used  again  till  laid  in  its  improved  form. 

Concrete  was  first  used  in  London  as  a  base  for  pavements  in 
1872,  and  the  custom  was  general  in  1875. 

In  Liverpool  granite  blocks  were  first  laid  in  1871,  and  wood 
in  1873. 

Tar  and  gravel  joints  for  stone  pavements  were  adopted  in  Lon- 
don in  1869,  and  in  Liverpool  in  1872,  though  they  had  previously 
been  in  use  in  Manchester. 

Glasgow  first  used  granite  block  and  wood  for  pavements  in 
1841,  and  asphalt  in  1873. 

Recent  excavations  show  that  the  streets  of  Pompeii  were  paved 
with  lava  from  Vesuvius.  The  pavement  must  have  been  laid  some 
time  previous  to  its  destruction,  as  the  blocks  in  many  places  show 
an  appreciable  wear,  although  the  traffic  must  have  been  very 
slight  when  compared  with  modern  times. 

Sienkiewicz  in  his  historical  novel  "  The  Deluge  "  says  that  the 
capital  of  Lithuania  was  paved  with  stone  in  1655,  and  adds  that 
this  was  something  extraordinary  for  that  time. 

A  history  of  Spanish  times  in  the  West  Indies,  after  describing 
a  visit  of  the  pirates  to  Porto  Bello,  Venzuela,  in  1668,  says:  "  Hav- 
ing stripped  the  unfortunate  city  of  almost  everything  but  its 
tiles  and  paving-stones,  the  sea-rovers  departed." 

Although  Paris  had  some  pavements  before  London,  it  was 
many  years  before  its  streets  were  in  even  a  decent  condition. 

Martin  Lister,  writing  of  Paris  in  1698,  says:  "  The  pavements 
of  the  streets  are  all  of  square  stones  of  about  eight  or  ten  inches 
thick;  that  is,  as  deep  in  the  ground  as  they  are  broad  on  top,  the 
gutters  shallow  and  laid  round  without  edges,  which  makes  the 
coaches  glide  easily  over  them."  On  another  page  he  says  the 
material  was  a  very  hard  sandstone,  and  that  all  the  streets  and 
avenues  were  paved. 

Aaron  Burr  in  1811  thus  describes  their  condition  in  a  letter 
to  a  friend:  "No  sidewalks — the  carts,  cabriolets,  and  carriages  of 
all  sorts  run  up  to  the  very  houses.  Most  of 


8  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

pun.,  up--to--t4ie— ve^Jimises.  Most  of  the  streets  are  paved  as 
Albany  and  New  York  were  before  the  Eevolution,  some  arched 
in  the  middle,  and  a  little  gutter  on  each  side  very  near  the 
houses.  It  is  fine  sport  for  the  cabriolets  or  hack-drivers  to  run  a 
wheel  in  one  of  these  gutters,  always  full  of  filth,  and  bespatter 
fifty  pedestrians  who  are  braced  against  the  wall." 

A  sample  of  asphalt  macadam  was  laid  on  the  road  between 
Bordeaux  and  Eouen  in  1840.  This  was  a  mixture  of  asphalt  rock 
and  ordinary  stone,  and  was  probably  the  first  bituminous  roadway 
laid  on  a  public  highway,  although  about  the  same  time  asphaltic 
rock  was  used  for  sidewalks  on  some  of  the  streets  of  Paris. 

In  1837  a  Mr.  Claridge  obtained  a  patent  for  using  Seyssel 
asphalt  for  paving  purposes  in  the  Departement  de  VAin. 

In  1854  the  Eue  Bergere  was  paved  with  compressed  asphalt, 
followed  by  the  Eue  St.  Honore  in  1858,  from  which  time  the  suc- 
cess *of  asphalt  pavements  has  been  assured  in  Paris. 

In  the  ruins  of  the  ancient  city  of  Palenque,  Mexico,  pave- 
ments of  cut-stone  blocks  have  been  discovered  which  must  have 
been  laid  at  a  very  early  period. 

In  the  city  of  Mexico,  from  a  very  early  date,  cobblestones  were 
used  for  pavements,  and  their  use  was  continued  till  1884,  when 
a  portion  of  the  principal  avenue  of  the  city  was  paved  with  stone 
Hocks.  The  stone  being  of  a  poor  quality,  the  result  was  not 
satisfactory  and  the  attempt  was  not  repeated.  Some  five  years 
later  wooden  blocks  were  tried,  but  the  expansion  was  so  great  that 
the  surface  was  deformed,  and  the  experiment  failed.  Lumber  being 
so  expensive  in  Mexico,  no  further  attempt  was  made  with  wood. 

In  1889  some  coal-tar  pavement  was  laid,  resulting  in  the 
usual  failure,  it  being  entirely  torn  up  a  year  later  and  asphalt 
blocks  substituted.  Up  to  1899  some  148,000  square  yards  of  this 
material  had  been  used  upon  a  cobblestone  and  sand  base  with 
"very  satisfactory  results.  Practically  all  the  pavement  in  the  city 
except  this  is  cobblestone. 

In  the  United  States  pavements  of  cobblestone  were  laid  in 
New  York  and  Boston  at  about  the  same  time. 

Of  the  former  city  Mrs.  John  King  Van  Eensselaer  in  her 
popular  novel  "  The  Goode  Vrowe  of  Manahatta  "  says  that  in  the 
early  days  of  New  York  the  Dutch  built  several  breweries  on  the 


THE  HISTORY  AND  DEVELOPMENT  OF  PAVEMENTS.         9 

road  lying  between  Broad  and  Whitehall  streets,  since  called  Brower 
Street.  The  good  housewives,  annoyed  by  the  dust  raised  by  the 
heavy  brewery  wagons,  made  frequent  complaints  to  the  city  authori- 
ties, who  finally  paved  the  roadway  with  small  round  stones.  This 
created  the  greatest  interest,  and  many  visitors  came  to  see  the 
"  stone  road,"  which  finally  came  to  be  and  is  now  known  as 
Stone  Street.  This  was  about  1656. 

In  Mrs.  Lamb's  "  History  of  New  York  "  it  is  stated  that  De 
Hoogh  Street,  now  Stone  Street,  was  paved  in  1656;  that  the 
second  was  Bridge  Street,  in  1658;  and  that  in  1660  all  the 
streets  most  used  were  paved  with  cobblestones,  the  gutter  being 
in  the  centre  of  the  street,  but  no  attempt  was  made  to  lay  side- 
walks. 

A  Swedish  traveller,  writing  of  New  York  in  1751,  says:  "  The 
streets  do  not  run  so  straight  as  those  of  Philadelphia  and  have 
sometimes  considerable  bendings;  however  they  are  very  spacious 
and  well  built,  and  most  of  them  are  paved  except  in  high  places, 
where  it  has  been  found  useless." 

In  New  York  cobblestones  were  almost  the  only  paving  material 
until  1849,  although  some  experimental  wooden  blocks  were  laid 
on  lower  Broadway  as  early  as  1835.  On  this  same  street  "  Russ  " 
blocks  were  laid  up  as  far  as  Franklin  Street  in  1849.  These 
blocks  came  from  Staten  Island  and  were  from  2  to  3  feet  square. 
In  1855  the  blocks  on  the  grades  were  grooved  to  give  better  foot- 
hold to  the  horses.  This  pavement  was  replaced  by  the  so-called 
Guidet  blocks  in  1868  or  1869. 

A  detailed  report  of  the  Council  of  Hygiene  and  Public  Health 
made  January  1,  1865,  says  that  practically  all  of  the  New  York 
pavements  of  that  date  were  cobblestone  or  Belgian  block.  There 
was  some  Euss  and  a  small  piece  of  cast-iron  block  on  Cortlandt 
Street. 

Belgian  blocks  were  first  .laid  on  the  Bowery  in  1852,  and  came 
into  very  general  use  after  1859.  They  made  the  improved  pave- 
ment of  the  times. 

The  present-shaped  granite  blocks  were  first  used  in  1876  or 
1877,  though  the  Guidet  patent  blocks  had  been  used  a  few  years 
previously.  This  latter  had  also  been  adopted  to  some  extent  in 
Brooklyn,  but  never  came  into  very  general  use.  Its  principal 


10  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

difference  from  the  present  pavement  was  in  the  size  of  the  blocks, 
they  being  very  large.  Some  of  them  measured  on  Atlantic 
Avenue,  Brooklyn,  in  1899  were  5  and  6  inches  wide  and  18  and  20 
inches  long. 

The  Dock  Department  used  tar  and  gravel  joints  for  a  granite 
pavement  on  a  sand  foundation  on  Pier  A,  North  Kiver,  in  1881, 
while  the  first  concrete  base  for  stone  was  regularly  used  in  1888 
in  the  city  streets.  A  small  piece  of  asphalt  was  laid  near  the 
Battery  in  1871. 

A  general  scheme  for  the  improvement  of  the  pavements  of 
New  York  was  adopted  in  1889.  This  was  made  possible  by  the 
legislation  obtained  the  previous  winter  authorizing  the  issue  of 
bonds  for  that  work. 

The  first  street  paved  in  Boston  was  probably  Washington 
Street,  about  1650,  the  material  being  "  pebbles/'  A  portion  of 
State  Street  was  paved  previous  to  1684,  and  quite  an  amount  of 
pavement  was  laid  in  the  latter  part  of  the  seventeenth  century. 
Many  of  the  original  paving  petitions  are  now  on  file  in  the  City 
Clerk's  office,  one  bearing  the  date  of  1714. 

Drake's  "  History  of  Boston  "  says  that  on  March  9,  1657,  the 
General  Court  ordered  "  the  paved  lane  by  Mrs.  Shrimpton's  to  be 
laid  open  and  no  more  to  be  shut  up."  This  is  the  year  following 
the  laying  of  the  first  pavement  in  New  York,  and  would  indicate 
that  Boston  began  the  work  of  paving  as  soon  as,  if  not  sooner  than, 
New  York. 

Speaking  of  Boston  in  1673:  "  Yet  for  several  years  after  this 
there  were  no  streets  paved  excepting  a  few  sections  of  some  of 
the  principal  ones,  and  those  of  a  few  rods  in  extent." 

On  April  19,  1704,  £100  was  voted  for  paving  "  such  places  of 
the  streets  as  the  selectmen  should  judge  most  needful,  and  therein 
to  have  particular  regard  to  the  Highway  near  old  Mrs.  Stoddard's 
"house." 

On  March  29,  1706,  £100  was  voted  "for  paving  the  Mayn 
street  towards  the  Landing  to  the  south  end  of  the  Town,  and  £50 
for  paving  at  the  lower  end  of  the  Town  house." 

In  1719  the  General  Court  authorized  the  town  to  raise  $2100 
by  a  lottery  towards  paving  and  repairing  the  Neck,  and  soon  after- 
wards authorized  another  to  raise  funds  for  paving  the  highway 


THE  HISTORY  AND  DEVELOPMENT  OF  PAVEMENTS.      11 

from  Boston  line  to  Meeting  House  Hill  in  Roxbury.  Winter 
Street  was  paved  about  1743. 

ShutlifFs  "  History  of  Boston  "  says:  "  In  the  year  1758  the 
townspeople  began  to  pave  the  streets  leading  to  the  Neck  partly 
at  the  expense  of  the  town  and  partly  by  private  subscription." 

Baltimore  paved  its  first  street  in  1781,  using  the  ever-present 
cobblestones,  which  in  1899  composed  about  75  per  cent  of  its 
entire  pavement. 

Philadelphia.  In  1726  a  Friend  relates  that  he  saw  paved  streets 
near  the  court-house  and  Market  House  Square.  Second  Street 
from  High  to  Chestnut  Street  was  the  first  one  regularly  paved. 
In  1719  a  gentleman  writing  to  his  brother  in  England  says:  "As 
to  bricks,  we  have  been  upon  regulating  our  pavements  of  our 
streets,  the  footway  with  bricks  and  the  cartway  with  stones,  which 
has  made  our  bricks  dear." 

About  the  same  time  the  minutes  of  the  City  Council  state  that, 
as  several  inhabitants  have  paved  the  streets  with  pebbles,  an 
ordinance  is  recommended  restraining  the  weights  of  loaded  car- 
riages passing  over  them.  In  1761-2  an  act  was  passed  "  Regu- 
lating, pitching,  paving  and  cleansing  the  highways,  streets,  lanes, 
and  alleys  &c  within  the  settled  parts  of  Philadelphia."  Curbstones 
were  first  adopted  in  1786. 

Philadelphia  claims  to  have  had  macadam,  or  broken  stone, 
streets  or  roads  two  hundred  years  ago,  and  was  probably  the  pio- 
neer in  this  country  in  that  respect.  Several  streets  were  paved  with 
hemlock  blocks  in  1839  and  1840,  but  with  little  success. 

In  1884  Philadelphia  had  535  miles  of  pavements,  of  which 
93  per  cent  was  cobble,  6J  per  cent  granite,  and  2  j  per  cent  asphalt. 
The  granite,  however,  was  not  the  present-shaped  blocks,  but  prac- 
iically  like  Belgian. 

In  that  year  a  special  commission  of  experts  was  appointed  to 
report  on  the  best  material  for  street  pavements,  and  the  era  of  im- 
proved streets  in  that  city  began  with  the  adoption  and  carrying 
out  of  the  commissioners'  report. 

Chicago.  In  Chicago  all  street  improvements  previous  to  1844 
consisted  in  keeping  the  earth  roadways  in  as  good  a  condition  as 
possible.  From  1844  to  1855  the  roadways  of  the  most  important 


12          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

streets  were  planked.    In  1855  1.72  miles  of  actual  pavement  was 
laid,  but  of  what  material  the  reports  do  not  state. 

San  Francisco.  In  the  big  fire  that  occurred  in  San  Francisco 
in  1850,  many  planked  streets  were  set  on  fire  and  consumed. 

Roads  constructed  for  short  distances  of  natural  asphalt  in 
southern  California  had  been  known  for  a  long  time  prior  to 
1870. 

New  Orleans.  New  Orleans  constructed  her  first  pavements 
of  cobblestones  in  1817,  when  the  population  of  the  city  was  about 
41,000.  Previous  to  this  time  it  had  not  been  deemed  practicable 
to  lay  a  pavement  successfully  on  the  soft  yielding  soil  of  the 
city.  A  general  paving  ordinance  was  passed  in  1822,  and  under 
its  provisions  streets  were  improved  with  shells,  cobble,  square 
blocks,  and  irregular  flat  stones. 

In  1837  an  ordinance  ordered  certain  streets  paved  with  the 
"  gunnels  "  of  flat  boats,  although  they  had  been  used  previous  to- 
that  time. 

In  1838  a  portion  of  St.  Charles  Street  was  paved  one-third 
with  stone  blocks,  one-third  with  curbstones  laid  flat,  and  one-third 
with  hexagonal  pine  blocks.  The  stone  and  wood  blocks  were  sat- 
isfactory, and  their  use  was  continued. 

A  bituminous  pavement  of  some  kind  was  laid  an  Gravier 
Street  in  1880,  but  proved  a  failure.  Asphalt  was  first  laid  on 
St.  Charles  Street  in  1885. 

From  1889  to  1896  a  number  of  streets  were  paved  with  gravel 
concrete,  but  the  material  did  not  give  good  satisfaction. 

Brick  was  used  in  1894,  and  chert  in  1895. 

The  dimensions  of  granite  blocks  were  14  x  10  x  88  inches. 

Cleveland.  The  first  stone  pavements  of  Cleveland  were  con- 
structed between  1851  and  1854,  of  Independence  sandstone.  The 
blocks  had  a  surface  of  8  or  10  by  12  inches  and  were  from  8  to  12 
inches  deep. 

Medina  sandstone  was  first  used  in  1856,  'and  the  streets  then 
paved  were  in  good  condition  in  1880. 

Nicholson  pavement  was  laid  in  1866.  In  1873  an  experiment 
was  tried  by  laying  a  mixture  of  coal-tar  and  roofing-gravel  to  a 
depth  of  three  inches  on  six  inches  of  broken  stone.  The  results- 
were  not  good. 


THE  HISTORY  AND  DEVELOPMENT  OF  PAVEMENTS.      13 

St.  Louis.  Main  Street  in  St.  Louis  was  paved  with  stone  in 
1818.  The  blocks  were  roughly  dressed,  irregular  in  shape,  from 
3  to  12  inches  thick,  6  to  14  inches  long,  and  6  to  10  inches  deep, 
and  set  on  6  inches  of  sand.  In  1842  the  specifications  called  for 
a  regular  block  4  to  5  inches  thick,  7  to  12  inches  long,  and  10 
inches  deep,  set  on  7  inches  of  gravel. 

Macadam  was  adopted  in  1832. 

Wood  has  been  experimented  with  in  St.  Louis  to  a  great  ex- 
tent. In  1851  and  1852  many  streets  were  planked.  In  1867 
Burnettized  cottonwood  was  used.  This  pavement  lasted  about 
seven  years,  when  it  was  replaced  with  untreated  pine,  which  had 
about  the  same  life. 

Cobblestones  were  tried  in  1855,  but  never  came  into  general 
use. 

Granite  and  asphalt  blocks  were  adopted  in  1873,  and  sheet 
asphalt  in  1883. 

Albany.  In  September,  1704,  the  City  Council  passed  the  fol- 
lowing resolution :  "  It  is  also  ordered  that  ye  streets  be  paved 
before  each  inhabitant's  door  within  this  citty,  eight  foot  breadth 
from  their  houses  and  lotts  before  ye  25th  of  October  next  ensueing, 
upon  penalty  of  forfeiting  the  summe  of  15s.  for  ye  behoofe  of  ye 
Sheriffe,  who  is  to  sue  for  ye  same." 

In  connection  with  the  visit  of  Peter  Kalm  in  1749  it  is  stated 
that  "the  streets  are  broad  and  some  of  them  are  paved/'  In 
1764  it  appears  from  Mrs.  Grant's  "Memoirs  of  an  American 
Lady"  that  State  Street  was  only  paved  on  each  side,  the  middle 
being  occupied  with  public  edifices.  Active  paving  work  was  not 
begun  till  about  1791,  when  Broadway  was  paved  and  complaint 
was  made  about  the  quantity  of  stones  required,  as  "  it  swallowed 
up  thousands  of  cartloads."  Cobblestones  were  the  only  material 
used  for  years,  dimension  granite  blocks  having  been  not  adopted 
until  1873. 


CHAPTEK  II. 

STONE. 

THE  rocks  that  once  formed  the  crust  of  the  earth  were  com- 
posed almost  entirely  of  nine  elements,  oxygen,  silicon,  magnesium, 
aluminum,  calcium,  iron,  sodium,  potassium,  and  carbon,  the  whole 
making  97.7  per  cent  of  the  earth's  crust. 

These  elements  combining  in  different  ways  formed  minerals, 
and  these  minerals  make  the  different  rocks  according  to  the  num- 
ber and  quantity  of  their  components. 

Rock  can  be  defined  as  any  material  forming  a  portion  of  the 
earth,  whether  hard  or  soft.  Rocks  are  divided  into  two  general 
classes,  stratified  and  unstratified.  Stratified  rocks  are  more  or  less 
consolidated  sediments  and  are  of  aqueous  origin.  Unstratified 
rocks,  having  been  more  or  less  completely  fused,  are  crystalline  in 
form  and  of  igneous  origin. 

The  igneous  rocks,  while  not  all  granite  in  the  strictest  sense, 
may  be  called  granitic,  for  they  are  granular  and  made  up  gener- 
ally of  the  same  substances  as  the  granites,  varying  in  their  propor- 
tions and  structure. 

The  minerals  forming  these  rocks  are  generally  considered  as 
being  divided  into  essential  parts  and  characterizing  and  micro- 
scopic accessories.  These  terms  are  self-explanatory,  the  essential 
parts  making  up  the  body  of  the  stone,  the  characterizing  accessory 
defining  its  exact  variety,  and  the  microscopic  being  those  con- 
tained in  very  minute  quantities. 

The  important  minerals  that  make  up  these  rocks  are  quartz, 
feldspar,  amphibole,  pyroxene,  and  mica. 

Quartz. 

Quartz  is  a  pure  silica,  composed  of  silicon  and  oxygen;  its 
specific  gravity  is  2.65  and  it  is  a  hard  and  brittle  mineral.  It  is 

14 


STONE.  15 

always  found  of  the  same  composition  and  hardness,  although,  the 
shape  of  its  particles  varies  considerably.  It  is  practically  indestruc- 
tible by  the  forces  of  nature,  which  accounts  for  its  forming  so  large 
a  proportion  of  all  sands.  Those  found  on  the  seashore  axe 
nearly  all  quartz.  When  absolutely  pure,  quartz  is  colorless,  but 
sometimes  it  contains  impurities  enough  to  give  it  a  color,  when  it 
is  known  as  rose  quartz,  smoky  quartz,  etc.,  according  to  its  appear- 
ance. When  it  is  in  a  metamorphic  state  with  its  crystals  cemented 
together  with  quartz,  it  forms  a  rock  called  quartzite. v 

Feldspar. 

Feldspar  is  an  anhydrous  silicate  of  alumina  together  with 
soda,  potash,  or  lime.  It  is  generally  softer  than  quartz,  with  a 
specific  gravity  of  from  2.4  to  2.6.  There  are  several  varieties  of 
feldspar;  the  principal  ones  being  orthoclase,  microcline,  albite, 
oligoclase,  and  labradorite.  It  is  also  divided  into  two  groups  ac- 
cording to  its  crystallization,  the  monoclinic  and  the  triclinic.  The 
former  contains  principally  silica,  alumina,  and  potash;  the  latter 
with  the  exception  of  microcline,  which  chemically  is  almost  the 
same  as  the  monoclinics,  has  no  potash,  but  in  its  stead  sodium  and 
lime.  According  as  the  above  constituents  vary  in  quality  and 
quantity,  the  feldspars  vary  in  hardness  and  color,  and  when  they 
are  in  appreciable  quantities  they  have  an  important  "bearing  on 
the  resulting  rock.  It  is  susceptible  to  the  action  of  the  elements, 
all  clays  being  formed  by  the  decomposition  of  feldspar. 

Amphibole. 

This  mineral  is  sometimes  called  hornblende,  which  term  really 
belongs  to  but  one  variety,  of  which  there  are  two,  the  aluminous 
and  the  non-aluminous.  The  former  contains  about  45  per  cent  of 
silica,  17  of  magnesia,  10  of  alumina,  12  of  lime,  and  16  of  iron 
oxides;  the  latter  57  per  cent  of  silica,  26  of  manganese,  14  of  lime, 
with  small  amounts  of  oxide  of  iron  and  manganese.  Hornblende 
belongs  to  the  aluminous  variety.  Hornblende  is  hard  and  tough 
and  imparts  these  characteristics  to  all  rocks  of  which  it  becomes 
a  part.  It  is  found  in  some  metamorphic  rocks.  Its  color  is  gen- 
erally a  brownish  green. 


16          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Pyroxene. 

Pyroxene  is  more  brittle  than  hornblende  and  consequently  not 
so  desirable  a  constituent  for  a  rock.  Its  principal  variety,  augite, 
is  an  essential  ingredient  of  diabase  and  basalt  and  also  an  acces- 
sory. It  is  dark-colored  and  composed  approximately  of  silica  50 
per  cent,  alumina  6  per  cent,  magnesia  15  per  cent,  lime  23  per 
cent,  and  iron  oxides  6  per  cent. 

Mica. 

This  is  the  mineral  so  well  and  popularly  known  as  isinglass. 
There  are  several  varieties,  but  the  two  found  in  granite  rocks  are 
muscovite  and  biotite.  They  are  always  found  in  thin  sheetlike 
forms  and  are  important  factors  in  the  make-up  of  rock,  both  as 
to  color  and  structure.  They  are  influential  disintegrating  agents, 
as,  on  account  of  their  laminations,  they  often  allow  the  entrance 
of  moisture,  which  is  an  important  element  of  decay  in  any  mate- 
rial. If  the  mica  is  deposited  in  different  layers  or  planes,  the  rock 
readily  splits  along  these  planes.  If  muscovite  is  the  variety  present, 
the  rock  is  generally  light-colored,  while  the  black  biotite  imparts 
its  color  to  the  stone,  often  giving  it  a  speckled  appearance.  Mus- 
covite is  a  silicate  of  potash  and  alumina,  and  biotite  of  alumina,, 
iron,  and  magnesia. 

Having  somewhat  hastily  examined  these  mineral  constituents 
of  the  granite  rocks,  it  will  now  be  in  order  to  take  up  the  rocks 
themselves.  They  are  complex  in  their  composition  and  structure, 
having  been  formed  at  different  times  and  under  different  condi- 
tions; some  containing  but  few  and  others  many  minerals,  often 
grading  into  each  other  so  imperceptibly  that  it  is  sometimes  al- 
most impossible  to  determine  where  one  variety  ends  and  the  other 
begins.  For  this  reason,  and  on  account  of  the  different  definitions 
given  to  the  same  variety  by  equally  good  authorities,  it  seems- 
proper  to  treat  these  rocks  as  one  class,  each  according  to  its 
characteristics,  and  not  attempt  to  make  any  arbitrary  class  dis- 
tinctions. 

The  group  of  rocks  which  it  is  proposed  to  study  in  this  con- 
nection may  be  defined  as  silicious,  holocrystalline,  granular  rocks. 
Their  essential  constituents  are  quartz  and  feldspar,  and  the  char- 
acterizing accessories  hornblende,  pyroxene,  and  mica,  with  some 


STONE.  IT 

other  less  important  minerals.  Microscopic  accessories  occur,  but 
in  such  small  quantities  that  they  will  not  be  taken  up.  In  some 
varieties  hornblende  and  pyroxene  are  considered  essential. 

Granite,  according  to  Dana,  consists  of  quartz,  feldspar,  and 
mica.  Under  this  definition,  no  stone  could  be  a  granite  unless 
it  contained  mica,  but  as  the  term  is  used 'commercially  it  includes 
syenite  and  gneiss  and  often  porphyry.  The  order  of  the  consolida- 
tion of  rocks  is  an  important  factor  in  their  structure.  As  a  rule, 
in  granite  the  minor  accessory  minerals  crystallized  first,  taking 
their  natural  form.  According  to  some  authorities  the  ferro- 
magnesian  minerals  came  next,  followed  by  the  feldspars,  and  lastly 
by  the  quartz  flowing  in,  filling  all  the  interstices,  making  a  com- 
plete and  solid  rock.  Occasionally,  however,  quartz  and  feldspar 
are  found  completely  intermingled,  indicating  that  they  crystallized 
at  the  same  time. 

While  the  character  of  a  granite  is  determined  principally  by 
its  essentials,  the  accessories  have  much  to  do  with  its  quality.  The 
color  is  generally  fixed  by  the  feldspar,  but  the  mica  is  often  a 
governing  characteristic,  the  presence  of  muscovite  making  a 
granite  light,  while  biotite  has  always  the  opposite  effect.  A  large 
amount  of  quartz  will  make  a  granite  hard  and  brittle,  while  too 
much  feldspar  renders  it  softer  and  tougher,  but  more  liable  to 
decomposition.  The  susceptibility  to  polish  and  its  ability  to  resist 
the  action  of  the  elements  depend  greatly  upon  the  accessory  com- 
ponents. Hornblende  is  a  mineral  which  permits  a  granite  to 
take  a  high  polish,  while  pyroxene,  being  very  brittle,  often  breaks 
out  when  a  stone  is  being  hammer-dressed,  giving  a  pitted  appear- 
ance to  an  otherwise  smooth  surface.  Iron  is  detrimental,  as  by 
the  action  of  the  weather  iron-rust  is  formed,  and  rains  washing 
it  over  the  surface  of  the  stone  produce  stains  upon  any  structure 
built  of  stone  containing  iron.  The  size  of  the  particles  of  the 
minerals  is  important.  The  smaller  the  grains  and  the  more  evenly 
they  are  distributed,  the  better  the  stone  will  cut  and  be  polished. 
The  finer  the  grain  the  better  satisfaction  the  granite  will  give  in 
cut  work.  A  fine-grained  stone  is  compact  in  texture,  excluding 
air  and  moisture,  two  agents  that  are  constantly  at  work  to  destroy 
all  minerals.  Granite  is  divided  into  varieties  according  to  the 
presence  of  its  varying  accessories. 


18          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Muscovite  granite  is  so  called  from  the  mica  being  of  the  musco- 
vite  variety.  It  is  not  found  in  large  quantities  in  this  country, 
but  is  produced  to  some  extent  from  the  quarries  of  Barre,  Vt. 

Biotite  granite  is  similar  to  the  above  except  that  the  muscovite 
is  replaced  by  biotite.  On  this  account,  while  the  former  is  always 
light  in  color,  the  latter  varies  from  light  to  dark  according  to  the 
quantity  of  mica  or  the  color  of  the  feldspar.  This  class  of  stone 
is  often  red,  owing  to  the  red  feldspar.  As  a  rule  the  stone  is  hard 
and  tough.  Good  samples  of  it  are  found  at  Westerly,  R.  I.,  and 
Dix  Island,  Me. 

Muscovite  Hotite  granite  stands  between  the  two  last  described, 
having  both  varieties  of  the  mica,  and  differing  from  them  only  in 
that  respect.  It  is  found  at  Concord  and  several  other  places  in 
New  Hampshire. 

Hornblende  granite  is  a  variety  in  which  the  characterizing 
accessory  is  almost  entirely  hornblende.  Biotite  is,  however,  gen- 
erally found  upon  a  microscopic  examination.  When  the  mica  can- 
not be  discovered  by  the  unaided  eye  the  name  "  hornblende  "  is 
given  to  the  variety.  Examples  of  this  are  found  at  Peabody,  Mass., 
and  Mt.  Desert,  Me. 

Hornblende-biotite  granite  is  distinguished  from  the  above  in 
that  it  contains  as  essentials  quartz  and  feldspar  with  both  horn- 
blende and  biotite.  This  combination  gives  a  dark  and  sometimes 
an  almost  black  granite,  capable  of  receiving  a  fine  polish. 

Examples  of  this  stone  are  found  at  St.  George,  Me.,  Cape  Ann, 
Mass.,  and  at  Sauk  Rapids,  Minn. 

One  important  property  that  is  possessed  by  all  granites  is  that 
of  splitting  more  easily  in  one  direction  than  another,  so  that 
it  is  easy  to  get  out  blocks  large  or  small  with  practically  parallel 
sides.  This  property  is  generally  called  rift  or  cleavage.  It  was 
caused  by  pressure  before  the  rock  was  consolidated.  The  rift  is 
always  perpendicular  to  the  line  of  pressure.  When  a  stone  is 
resting  upon  a  face  parallel  to  its  cleavage  plane  it  is  said  to  be 
lying  on  its  bed,  and  the  face  at  right  angles  to  the  bed  is  called 
the  edge.  Rift  is  governed  by  the  amount  of  pressure  and  the  grain 
of  the  stone,  so  that  while  all  granites  have  a  rift  they  do  not  have 
it  in  the  same  degree.  The  finer-grained  granites  have  the  best 
rift,  decreasing  as  the  grains  increase,  so  that  a  coarse-grained 


STONE.  19 

variety  is  apt  to  be  bunchy  and  requires  considerable  dressing  to 
bring  the  faces  of  the  block  to  a  plane  surface.  This  fact  is  well 
known  to  quarrymen,  and  an  experienced  hand  will  easily  and 
quickly  tell  the  character  of  the  rift  by  the  general  appearance  of 
the  stone. 

Although  it  has  been  said  that  granite  breaks  more  easily  in 
one  direction  than  another,  on  account  of  its  peculiar  structure  it 
can  be  broken  into  blocks  of  almost  any  shape  by  skilled  workmen 
with  a  stone-hammer,  or  with  proper  wedges  and  lewises  if  a  large 
and  irregular  block  be  required.  By  this  method  the  dividing  force 
is  exerted  in  whatever  direction  desired  by  inserting  the  wedges  and 
lewises  into  holes  drilled  for  the  purpose,  when  by  lightly  driv- 
ing the  wedges  in  succession  the  quartz  which  is  holding  the  other 
crystals  together  is  easily  fractured  and  the  granite  breaks  as  de- 
sired. On  account  of  this  fact  it  is  particularly  adapted  for  paving- 
blocks  and  curbing,  as  it  is  cheaply  and  rapidly  formed  into  the 
proper  size  and  shape.  Often  a  stone  is  barred  from  use  as  a  pav- 
ing material  for  the  reason  that  so  much  work  is  required  to  get  it 
down  to  specification  size. 

Gneiss  is  a  variety  of  granite  which  differs  from  that  just  de- 
scribed only  from  the  fact  that  its  rift  is  caused  by  the  greater  por- 
tion of  its  mica  being  gathered  in  parallel  planes  so  that  the  stone 
is  easily  broken  along  these  planes.  This  is  purely  a  physical  dif- 
ference, as  chemically  and  mineralogically  it  is  the  same  as  granite 
proper.  This  'arrangement  of  the  mica  weakens  the  stone  appreci- 
ably when  set  on  edge,  a  fact  which  is  not  true  of  the  granites. 

Dana  defines  gneiss  as  consisting  of  quartz,  feldspar,  and  mica, 
and  possessing  cleavage  planes. 

Syenite,  according  to  Dana,  consists  of  feldspar  and  hornblende 
with  or  without  quartz.  It  will  be  noticed  that  the  mica  of  granite 
and  gneiss  has  disappeared  and  hornblende  has  taken  its  place. 
This  latter  mineral  is  hard  and  compact,  varying  considerably  in 
its  composition,  but  made  up  principally  of  silicate  of  magnesium 
and  calcium,  with  some  alumina  and  iron.  It  has  its  cleavage  in 
two  planes  and  is  easily  brought  to  a  fine  polish. 

In  1787  Werner  adopted  the  definition  quoted  above  from 
Dana,  but  later  German  geologists  have  used  the  term  syenite  to 
designate  rocks  without  quartz,  differing  only  from  granite  in  that 


20  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

respect  and  consisting  mainly  of  orthoclase  feldspar  in  company 
with  one  or  more  minerals  of  the  amphibole  (hornblende)  or  pyrox- 
ene group.  This  combination  has  seldom  been  used  or  found  in 
this  country. 

Porphyry. — The  mineral  and  chemical  composition  of  the  quartz 
porphyries  is  essentially  the  same  as  that  of  the  granites,  from 
which  they  differ  mainly  in  their  "  porphyritic  "  structure.  That 
is,  the  quartz  has  cooled  first,  thereby  gaining  -a  crystalline  form 
so  that  the  rock  presents  to  the  eye  a  dense  compact  mass  of  stone 
in  which  can  be  seen  crystals  of  quartz  alone  or  quartz  and  feldspar 
together.  This  structure  characterizes  all  the  rocks  of  this  type. 
The  ferromagnesian  minerals  are  often  confined  to  the  elements 
of  the  earlier  period  of  crystallization,  while  the  original  quartz 
is  found  in  the  acid  types  only,  and  is  generally  restricted  to  the 
ground-mass. 

This  change  of  structure  prevents  the  formation  of  the  rift  so 
characteristic  of  the  true  granites.  In  composition  it  is  generally 
about  two-thirds  silica. 

Diabase  (Trap-rock). — The  essential  constituents  are  plagioclase, 
feldspar,  and  augite,  with  nearly  always  magnetite  and  apatite  in 
small  proportions.  The  accessories  are  hornblende,  biotite,  olivine, 
etc.  It  is  holocrystalline  in  form,  but  not  often  having  perfect 
crystal  outlines,  as  they  are  more  or  less  distorted  on  account  of 
interference  during  the  process  of  formation.  The  feldspar  gen- 
erally crystallizes  before  the  ferromagnesian  constituent,  the  former 
being  often  found  wrapped  around  by  the  augite.  As  a  rule  it  is 
finer-grained  than  the  granites.  It  varies  in  color  according  to 
its  constituents  from  a  dark  gray  to  almost  black.  The  rock  is 
hard,  compact,  and  tough,  but  not  easily  broken  into  regular 
shapes.  It  occurs  in  dikes,  where  the  material  in  a  melted  state 
poured  into  the  fissures  already  created  and,  cooling,  there  divided 
masses  of  the  same  character  into  separate  and  distinct  parts.  This 
is  often  seen  in  limestone  formations  in  Maine.  The  best  illustra- 
tion of  trap-rock  in  this  country  is  probably  the  Palisades  of  New 
Jersey,  although  it  is  also  found  in  Connecticut,  Pennsylvania,  and 
Virginia.  It  has  a  specific  gravity  of  from  2.8  to  3.2. 

Basalt.— This  rock  does  not  differ  materially  from  diabase,  but 


STONE.  21 

is  of  more  recent  origin.  The  essential  minerals  are  augite  and 
plagioclase  feldspar  with  olivine.  The  accessories  are  different 
varieties  of  iron  and  apatite  with  sometimes  quartz,  mica,  etc. 
Structurally  it  varies  from  the  glassy  to  the  holocrystalline.  Chemi- 
cally it  is  composed  of  silica  50  per  cent,  alumina  14,  lime  10, 
magnesia  6,  oxide  of  iron  and  manganese  12,  and  soda  4  per  cent, 
with  small  quantities  of  potash,  etc.  In  the  United  States  it  is 
found  principally  west  of  the  Mississippi,  and  especially  in  Cali- 
fornia and  Oregon.  It  is  generally  finer-grained  than  trap-rock. 
It  was  used  very  generally  by  the  early  road-builders  of  the  old 
country,  being  carried  great  distances  to  form  the  surface  of  the 
roads  on  account  of  its  fine  wearing  qualities. 

Sioux  Falls  Stone. 

This  is  a  red  quartzite  or  metamorphic  sandstone.  It  contains 
85  per  cent  of  quartz-.  Its  color  is  due  to  oxide  of  iron.  It  is  said 
to  be  the  hardest  stone  in  the  country.  It  weighs  162  Ibs.  per  cubic 
foot  and  has  a  crushing  strength  of  28,000  Ibs.  per  inch.  On 
account  of  its  hardness  it  is  not  much  used  for  building  purposes, 
but  has  been  to  some  extent  in  Western  cities  for  pavements.  It 
wears  smooth  with  a  glassy  surface. 

ANALYSIS   OF   GRANITE  FROM  PORT  DEPOSIT,  MD. 

Per  cent. 

Silica    73.690 

Alumina  12.891 

Ferric  iron 1.023 

Ferrous  oxide 2.585 

Lime    3.737 

Magnesia 498 

Potash   1.481 

Soda   2.811 

Water   1.060 

Total   99.776 

The  mineral  composition  of  this  rock  was  calculated  from  the 
above  analysis,  but  nothing  more  than  an  approximate  result  could 
be  expected  because  the  exact  composition  of  the  minerals  is  not 
known.  It  was  supposed  to  be: 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Per  cent. 

Biotite  9.7 

Feldspars 46.4 

Quartz 40.0 

Epidote  3.9 

100.0 
Itfi  crushing  strength  was  21,180  Ibs.  per  square  inch. 

GRANITE  FROM   WATERFORD,  CONN. 

Per  cent. 

Silica  68.11 

Alumina  14.28 

Ferrous  oxide 2.63 

Lime 1.86 

Magnesia 68 

Sulphur  34 

Oxide  of  potassium 5.46 

Oxide  of  sodium 6.57 


Total  99.93 

An  average  of  the  tests  made  of  this  stone  showed  a  crushing 
strength  of  23,715  Ibs.  per  square  inch. 

GRANITE  FROM  BLUE  HILL,  ME. 

Per  cent. 

Water  0.27 

Silica  74.64 

Ferric  oxide 1.56 

Alumina   14.90 

Lime 39 

Magnesia   Trace 

Potassium  oxide 6.88 

Sodium  oxide 41 

99.05 
Prom  this  analysis  the  mineral  composition  was  calculated  to  be: 

Per  cent. 

Mica  35 

Feldspar  10 

Quartz 55 

100 


STONE,  23 

GRANITE  FROM    NORTH   JAY,  ME. 

Per  cent. 

Silica 71.54 

Titanic  oxide  and  iron  peroxide 0.84 

Alumina   14.24 

Ferric  oxide 74 

Ferrous  oxide 1.18 

Lime 98 

Magnesia .34 

Soda   3.39 

Potash    4.73 

Water   61 

Sulphur  and  carbon  dioxide Trace 


98.59 

This  rock  is  described  as  an  even-grained  white  granite  com- 
posed of  white  feldspar,  quartz,  biotite,  and  muscovite,  with  a  small 
grain  of  red  garnet.  Its  name  is  biotite  muscovite  granite.  It 
showed  a  crushing  strength  of  16,310  Ibs.  per  square  inch. 

A  red  granite  from  the  same  place  had  a  strength  of  22,367  Ibs. 
per  square  inch. 

PINK   GRANITE   FROM   MILFORD,   MASS. 

Per  cent. 

Silica  76.07 

Alumina  12.67 

Ferric  oxide 2.00 

Oxide  of  manganese 03 

Lime ' 85 

Magnesia 10 

Potash   4.71 

Soda  3.37 

99.80 
Its  compressive  strength  was  20,883  Ibs.  per  square  inch. 

DARK  GRANITE  FROM  BARRE,  VT. 

Per  cent. 

Silica  69.56 

Ferric  oxide 2.65 

Alumina  15.38 

Manganese  Trace 


24          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Per  cent. 

Lime 1.76 

Magnesia Trace 

Sodium  oxide 5.38 

Potassium  oxide 4.31 

Loss  on  ignition 1.02 


100.06 

This  specimen  is  described  as  a  fine,  even-grained  typical  granite 
containing  both  biotite  and  muscovite  with  quartz  and  feldspar.  Its 
specific  gravity  is  2.672.  It  had  a  crushing  strength  of  17,254  Ibs. 
per  square  inch,  weight  applied  perpendicular  to  the  rift,  and 
19,957  Ibs.  parallel  to  rift. 

GRANITE   FROM   PETERSBURG,   VA. 

Per  cent. 

Silica  64.12 

Alumina   20.91 

Oxide  of  iron 2.96 

Lime    1.98 

Magnesia 66 

Sodium  oxide 4.57 

Potassium  oxide. .  4.82 


100.02 

Its  composition  was: 

Per  cent. 

Mica   15 

Feldspar   60 

Quartz    . 25 

100 

Its  crushing  strength  was  25,100  Ibs.  per  square  inch. 

GRANITE   FROM   QUINCY,  MASS. 

Per  cent. 

Silica  75.14 

Alumina 15.57 

Ferrous  oxide 2.49 

Lime  1.85 

Potash    54 

Soda  4.41 

100.00 

Its  mineral  constituents  are  principally  quartz,  hornblende,  and 
feldspar.    The  stone  is  very  hard  and  capable  of  receiving  a  high 


STONE.  25 

polish.    Its  crushing  strength  was  found  by  Gillmore  to  be  17,750 
Ibs.  per  square  inch,  and  its  specific  gravity  2.669. 

GRANITE  FROM   EXETER,  CAL. 

Per  cent. 

Silica    75.35 

Oxide  of  iron 3.94 

Oxide  of  aluminum 13.69 

Oxide  of  calcium 2.97 

Oxide  of  magnesium .06 

Oxide  of  sodium 1.14 

Oxide  of  potassium 2.85 


100.00 

This  stone  has  a  shearing  strength  of  2419  Ibs.  per  square  inch 
and  a  coefficient  of  expansion  of  0.00000461  per  inch.  Granite 
from  Millbridge  had  a  coefficient  of  expansion  of  0.000004  between 
32°  and  212°  F. 

The  total  value  of  the  granite  output  of  the  United  States  for 
the  years  1896  and  1897  is  $7,944,994  and  $8,905,075  respectively. 
Of  this  amount  nearly  one-half  was  furnished  by  the  States  of 
Massachusetts,  Maine  and  Vermont.  The  value  of  the  paving-blocks 
for  the  same  years  was'$l,231,736  and  $1,140,417.  In  1896  Maine 
furnished  $344,101  worth,  Massachusetts  $324,784,  and  Georgia 
$94,390;  while  in  1897  Georgia  supplied  $295,005  worth,  Massa- 
chusetts $243,750,  and  Maine  $172,637.  This  great  falling  off  in 
values  in  New  England  is  attributable  to  the  increased  use  of 
asphalt  for  pavements  in  cities  which  in  former  years  drew  largely 
from  the  New  England  quarries.  This  use  of  asphalt  not  only  de- 
creased the  quantity  of  granite  used,  but  also  the  value  per  thousand 
of  the  blocks  themselves. 

VALUE  OF   GRANITE  PRODUCT    1890  TO    1897. 

1890 $14,464,095 

1891 13,867,000 

1892 12,642,000 

1893 8,808,934 

1894 10,029,156 

1895 8,894,328 

1896 7,944,994 

1897 8,305,075  * 

*  One-fourth  for  building. 


26          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

ANALYSIS   OF    TRAP-BOCK   FROM   MERIDEN,   CONN. 

Per  cent. 

Silica 52.37 

Aluminum  oxide 15.06 

ferric    oxide 2.34 

Ferrous  oxide 9.82 

Titanium  oxide .21 

Manganous  oxide .32 

Magnesium    oxide 5.38 

Calcium  oxide 7.33 

Potassium  oxide 92 

Sodium  oxide 4.04 

Water  . ,  2.24 


100.03 


This  stone  had  a  crushing  strength  of  34,920  Ibs.  per  square 
inch  and  a  specific  gravity  of  2.965. 


TRAP-ROCK  FROM  MONSON,  MASS. 

Per  cent. 

Silica  * 52.59 

Ferric    oxide 14.55 

Alumina  23.42 

Lime    9.05 

Magnesia 28 

Manganous  oxide 09 


99.98 
Specific  gravity  3.01. 

BIRDSBOROTJGH  TRAP-ROCK,  PENN. 

Per  cent. 

Silica  46.87 

Alumina  13.36 

Ferrous  oxide 2.71 

Ferric  oxide 9.79 

Calcium  oxide 14.70 

Magnesium  oxide 4.35 

Sodium  oxide 4.64 

Potassium  oxide 2.01 

Titanium  oxide. .  1.98 


100.41 


STONE. 


From  the  above  and  microscopic  examinations  the  mineral  con- 
stituents were  found  to  be  plagioclase,  feldspar,  pyroxene,  and  horn- 
blende, with  4.56  per  cent  of  magnetite  or  .magnetic  iron.  This  is 
a  stone  similar  to  that  forming  the  Palisades  of  the  Hudson  in  New 
Jersey. 

TABLE  No.  1. 

ANALYSIS   OF   TRAP-ROCK  FROM   NEW  JERSEY. 

Per  cent. 

52.29 

14.30 

16.68 

9.35 


Per  cent. 

Silica  50.61 

Iron  13.91 

Alumina  18.34 

Lime    7.01 

Magnesia 6.73 

Potash    0.08 

Soda  1.60 

Water   .  1.72 


4.58 

0.48) 

2.80) 


Per  cent. 
50.03 
16.81 
18.20 
11.10 

1.02 

1.03 


Per  cent. 
51.20 
11.12 
20.88 
12.50 
2.17 
1.03 


100.00  100.48 

•  New  Jersey  Report,  1898. 

TABLE  No.  2. 


1.80 


100.00 


1.10 


100.00 


RESULTS   OP  TESTS  MADE  OP  CRUSHING   STRENGTHS  OF  DIFFERENT  GRANITES. 


Locality. 

Position. 

Authority. 

Bed.       Edge. 
23013    23049 

I.  H.  Woolson,  Col.  College 

Do               

22548    21699 

Do 

Do.              

31881     30996 

Do. 

Barre   Vt  

17254    19957 

Wm.  C.  Day  Swarthmore  Col 

Do         

16412    15845 

Do. 

26880 

Watertown  Arsenal 

Stone  Mt.,  Ga  
North  Jay   Me     white  

28953 
16310 

Do. 
Do 

Do              red  

22367 

Do. 

Westfield   Mass  

16091 

Do. 

Exeter,  Cal  

21104 

Do. 

Milford,  Mass  

20883 

Do. 

Port  Deposit,  Md     

21180 

Booth,  Garrett  &  Blair  Phil 

Brandywine  Granite  Co.*  
Mount  Airy,  N.  C  

25075 
20000 

Do. 
Richie  Bros.,  Phila. 

23715 

I.  H.  Woolson,  Col.  College 

•Graniteville,  Mo  

24749 

J.  B.  Johnson   Wash   Univ 

*  Gneiss. 

Sandstone. 

Sand  is  formed  by  the  decomposition  or  disintegration  of  rocks. 
It  is  a  common  occurrence  to  find  pockets  of  sand  in  beds  of  earth 
or  limestone.  These  are  the  result  of  boulders  being  surrounded 


28          STREET  PAVEMENTS  AND  PAVING  MATERIALS: 

when  these  deposits  of  clay  or  stone  were  first  made.  Long  after- 
wards the  boulders  decayed,  and  in  their  places  are  discovered 
pockets  of  sand.  Its  composition  depends  upon  the  minerals  con- 
tained in  the  original  rocks. 

When  large  deposits  of  stone  decay,  the  particles  of  quartz, 
being  indestructible,  are  borne  away  principally  by  two  agencies, 
water  and  the  winds.  At  this  time  the  different  products  are  often 
separated  and  the  quartz,  being  heavier  than  the  decomposed  min- 
eral, is  kept,  by  itself,  as  in  the  case  of  the  sands  of  the  seashore  and 
those  of  a  desert. 

Large  grains  are  as.  a  rule  affected  more  than  small  ones.  Sea 
sands  are  less  sharp  than  those  of  rivers  and  lakes,  on  account  of 
the  constant  action  of  the  waves  and  tides;  while  those  of  a  desert 
or  any  place  subject  to  the  action  of  the  winds  are  most  rounded 
of  all.  It  is  only  in  desert  sands  that  the  smallest  grains  show  any 
great  effect  of  attrition. 

Sandstone  is  formed  by  grains  of  sand  being  deposited  in  beds 
by  some  agency  and  afterwards  compacted.  The  sand  proper  is 
almost  all  quartz,  as  this  mineral  is  indestructible  from  the  ordinary 
action  of  the  elements,  while  the  cementing  portion  of  the  original 
rock  has  generally  been  decomposed  and  a  new  substance  formed. 
The  solidification  of  the  stone  is  caused  by  great  pressure,  partial 
solution,  fusion  of  some  of  its  own  parts,  or  by  the  infiltration  of 
some  cementing  material,  such  as  silica  lime,  or  the  oxides  of  iron. 
It  is  generally  found  in  layers  of  variable  thickness  separated  from 
each  other  by  some  softer  material.  The  thickness  of  these  layers 
probably  depends  upon  the  time  one  force  acted  continuously  upon 
the  sand,  the  softer  deposits  being  made  during  the  intervening 
period. 

The  texture  of  the  stone  varies  according  to  the  sizes  of  the 
sand-grains,  some  being  so  fine  as  to  be  barely  discernible,  while 
others  are  very  coarse,  with  every  gradation  between  them.  Mica 
and  feldspar  are  sometimes  ingredients,  and  upon  the  composition, 
as  well  as  the  cementing  material  with  which  it  is  held  together, 
depends  its  value  as  stone. 

Sandstones  are  of  many  colors,  the  most  common,  however, 
being  gray,  yellow,  and  red.  These  colors  are  determined  by  the 
different  combinations  of  iron;  the  red  being  due  to  peroxides,  and 


STONE.  29 

the  yellow  to  hydrous  peroxides.  Some  varieties  will  change  color 
upon  exposure  to  the  air  or  the  application  of  heat,  on  account  of 
the  oxidation  of  the  iron. 

When  the  rock  is  solidified  by  any  of  the  methods  mentioned 
above,  except  pressure,  the  cementing  substance  must  be  considered 
as  having  been  formed  in  place,  and  upon  its  complete  formation 
the  rock  may  be  said  to  have  entered  upon  a  new  era  in  its.  his- 
tory. 

When  the  cement  is  calcareous,  it  has  generally  been  deposited 
as  mud  or  pulverized  shells,  but  it  has  no  binding  properties  until 
it  has  been  partially  dissolved  and  redeposited  in  a  somewhat  crys- 
talline form.  This  cement  is  sometimes  mixed  with  red  oxide  and 
brown  hydrated  oxide  of  iron. 

In  the  hard  and  tougher  sandstones  the  cement  is  generally 
silicious.  If  the  grains  have  not  been  much  rounded  and  are 
of  irregular  size,  the  interstices  are  very  small  and  the  silica  is  of 
no  great  amount  and  often  hard  to  discover,  as  it  may  be  hidden 
by  dust  or  iron-stains.  When  the  spaces  are  comparatively  large 
the  silicious  cement  is  often  deposited  around  the  quartz-grains, 
increasing  their  size  and  completing  the  rock  by  a  regular  growth. 
Red  sandstones  are  sometimes  found  to  be  easily  disintegrated  on 
account  of  the  iron  oxide  separating  the  original  grains  from  the 
cementing  material. 

In  street  construction  sandstones  are  used  for  curbing,  cross- 
walks, flagging,  and  for  paving  the  roadway  of  the  street.  Those 
most  commonly  used  for  these  purposes  in  this  country  are  the  so- 
called  Hudson  River  bluestone,  Medina  sandstone,  Berea  grit,  and 
Colorado  sandstone.  The  Medina  stone  and  that  from  Colorado 
are  the  only  ones  of  these  used  in  pavements  proper. 

Hudson  River  Bluestone. 

This  variety  is  not  generally  considered  to  be  a  sandstone,  but 
is  known  commercially  in  the  localities  where  it  is  used  as  "  blue- 
stone."  It  is  very  hard  and  durable  and  is  used  almost  entirely 
for  curbing,  flagging,  and  cross-walks,  for  which  purpose  it  is  so 
well  adapted  on  account  of  its  great  transverse  strength.  It  is  also 
very  evenly  bedded,  so  that  its  surface  is  smooth,  making  it  espe- 
cially desirable  for  sidewalks. 


30  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

This  formation  extends  about  100  miles  in  New  York  from  the 
southwestern  towns  of  Albany  County  across  Greene,  Ulster, 
Orange,  and  Sullivan  counties  to  the  Delaware  Eiver.  The  land 
along  this  line  is  of  little  worth  for  any  agricultural  purposes,  its 
value  being  governed  by  the  amount  and  quality  of  the  stone  it  can 
produce.  The  different  quarries  vary  much  in  the  number  and 
thickness  of  the  quarry-beds,  as  well  as  the  amount  of  the  overlying 
earth.  The  beds  range  in  -thickness  from  an  inch  up  to  three  feet, 
and  irf  a  few  cases  to  six  feet,  the  thinner  layers  being  near  the 
surface. 

The  strata  can  generally  be  split  in  places  parallel  to  the  bedding 
and  to  the  required  thickness,  the  size  -of  the  pieces  being  deter- 
mined by  the  vertical  joints.  Stones  sixty  by  twenty  feet  have  in 
some  instances  being  obtained. 

The  product  of  the  different  quarries  varies  somewhat  in  color 
as  well  as  hardness  and  texture,  and  consequently  in  value.  The 
texture  ranges  from  the  fine  shaly  or  argillaceous  to  the  silicious 
and  even  the  conglomerate  rock.  The  best  is  fine-grained, 
not  very  plainly  laminated,  and  is  composed  almost  entirely  of 
silica  cemented  together  by  a  silicious  paste.  It  is  therefore  very 
hard  and  durable.  It  is  so  compact  that  it  absorbs  but  little  mois- 
ture and  dries  off  quickly  after  a  rain.  A  representative  specimen 
had  a  specific  gravity  of  2.751  and  contained  4.63  per  cent  of 
ferrous  and  0.79  per  cent  of  ferric  oxide.  It  absorbed  0.82  per 
cent  of  water.  At  a  temperature  of  from  1200°  to  1400°  F.  its 
color  changed  to  a  dull  red,  and  the  piece  was  slightly  checked  and 
its  strength  impaired. 

Stone  very  similar  to  the  Hudson  River  variety  is  found  in 
Luzerne  County,  Penn.  A  sample  of  this  being  analyzed  showed: 

Per  cent. 

Silica  and   insoluble  matter 94.00 

Ferric  oxide 1.98 

Lime    1.10 

Magnesia    1.00 

Water  and  carbonic  acid  (volatile  at  red  heat) 1.92 

Alumina Trace 


100.00 
Its  specific  gravity  was  2.656. 


STONE.  31 


Medina  Sandstone. 

This  stone  is  found  in  New  York  State,  extending  from  Oneida 
and  Oswego  counties  on  the  east  along  the  shores  of  Lake  Ontario 
westerly  to  the  Niagara  Kiver.  It  also  continues  on  into  Canada, 
and  is  found  to  some  extent  in  Pennsylvania  and  Virginia.  It  is 
of  the  Upper  Silurian  formation.  It  is  generally  a  deep  brownish 
red  in  color,  though  sometimes  light  and  yellowish,  and  in  a  few 
localities  gray.  The  coloring-matter  is  oxide  of  iron.  In  some 
instances  where  the  red  stone  joins  the  gray,  the  iron  has  pene- 
trated the  latter  to  quite  an  extent.  It  is  both  fine-  and  coarse- 
grained in  texture,  the  latter  being  of  a  deeper  color  as  the  iron 
cement  more  easily  penetrates  the  interstices  between  the  larger 
grains.  The  gray  stone  often  contains  marine  shells,  but  these 
are  rarely  found  in  the  red.  The  metals  in  composition  are  copper 
and  iron  pyrites,  oxide  of  manganese  and  iron,  and  carbonates  of 
copper.  Alternate  freezing  and  thawing  produce  but  little  change 
in  its  strength.  At  Fulton,  Oswego  County,  it  forms  the  banks 
and  falls  of  the  river,  and  is  noticeable  for  a  half  mile  below,  being 
formed  in  layers  about  two  feet  thick.  At  one  quarry  near  Lock- 
port  layers  are  found  varying  in  thickness  from  an  eighth  to  a 
quarter  of  an  inch  up  to  several  feet,  and  in  another  from  a  few 
inches  up  to  six  feet.  These  layers  are  easily  separated  from  each 
other,  as  they  are  partially  covered  with  oxide  of  manganese. 

On  the  Niagara  Kiver  the  stone  is  nearly  white,  but  on  going 
east  it  becomes  tinged  with  red,  and  at  Medina  the  layers  are  very 
strongly  colored,  and  sometimes  spotted  red  and  white. 

The  principal  mineral  constituent  is  quartz  associated  with 
some  kaolinized  feldspar.  The  cementing  material  is  mainly  oxide 
of  iron  with  some  carbonate  of  lime.  It  is  evenly  bedded,  and  the 
strata  dip  to  the  south.  The  beds  are  divided  into  blocks  by  sys- 
tems of  vertical  joints,  generally  at  right  angles  to  each  other, 
greatly  facilitating  the  work  of  quarrying. 

While  quarries  have  been  opened  in  many  counties,  the  principal 
ones  are  located  between  Brockport  and  Lockport  in  Monroe  and 
Niagara  counties.  At  Medina  the  stone  is  hard,  with  oblique 
laminations  in  the  bed.  The  gray  stone  is  nearly  all  used  for 


32  STREET  PAVEMENTS  AND  PAYING  MATERIALS. 

paving-blocks,  although  other  colors  are  so  used  as  well  as  for  flag- 
ging and  cross-walks. 

A  sample  from  Albion,  Orleans  County,  had  a  specific  gravity 
of  2.60.  It  had  0.51  per  cent  ©f  ferrous  and  0.06  per  cent  of  ferric 
iron  and  absorbed  2.37  per  cent  of  water.  One  from  Oswego  Falls 
had  a  specific  gravity  of  2.62  per  cent,  contained  0.59  per  cent  of 
ferrous  and  1.71  per  cent  of  ferric  iron,  and  absorbed  3.73  per  cent 
of  water. 

Potsdam  Sandstone. 

This  formation  is  the  oldest  of  any  in  New  York  in  which  sand- 
stone is  quarried.  It  is  found  in  several  counties  in  the  State.  It  is 
grayish,  yellow,  brown,  and  sometimes  red  in  color,  according  to 
the  amount  and  kind  of  iron  in  composition.  It  varies  from  a 
strong  compact  quartzite  to  a  loosely  coherent  granular  mass. 

The  largest  quarries  are  near  Potsdam,  hence  its  name.  This 
stone  is  hard  and  compact,  evenly  grained,  and  reddish  in  color. 
It  is  largely  used  as  a  building-stone  and  also  for  pavements. 

It  was  used  to  some  extent  in  the  Columbia  College  buildings. 

It  consists  almost  entirely  of  quartz,  the  grains  being  very  clear, 
many  of  them  showing  a  secondary  enlargement.  The  cementing 
material  is  almost  wholly  silica.  It  absorbed  2.08  per  cent  of  water, 
and  has  a  specific  gravity  of  2.6.  Under  the  heat  test  its  color  was 
unchanged.  No  checks  appeared,  and  its  strength  was  but  little 
impaired. 

Berea  Sandstone. 

This  stone  has  an  area  in  Ohio  alone  of  about  15,000  square 
miles,  and  it  also  extends  into  four  adjacent  States.  It  is  a  well- 
defined  deposit,  moderately  coarse-grained,  from  forty  to  sixty 
feet  thick.  It  is  generally  gray  in  color,  but  sometimes  spotted 
with  iron  stains,  and  in  some  localities  a  light  buff  or  drab.  It  is 
quarried  in  great  quantities  at  Berea,  Ohio,  whence  it  derives  its 
name  of  "  Berea  grit."  At  that  place  it  is  covered  by  the  Cuyahoga 
shale  and  by  drift  clay.  At  Peninsula,  however,  the  formation  is 
from  thirty  to  sixty  feet  above  the  canal,  making  the  quarrying 
work  very  easy.  It  is  of  great  value  for  building-stone,  as  it  is 


STONE.  33 

easily  gotten  out  into  regular  shapes  and  is  cut  without  difficulty. 
It  is  the  best  grindstone  grit  in  the  country.  It  is  sufficiently  por- 
ous below  the  surface  to  carry  petroleum,  gas,  etc.  It  is  too  soft 
for  paving  purposes,  but  is  used  very  generally  for  curbing  and 
nagging. 

The  formation  is  supposed  to  represent  an  old  shore-line,  as 
much  of  the  surface  is  ripple-marked  and  shows  many  signs  of 
worms.  An  analysis  of  an  average  sample  gave: 

Silica  96.90 

Iron  oxide .       1.68.  CRUSHING  STRENGTH. 

Lime    • .55 

Potash  and   soda 55  Bed 17,500 

Carbonic  acid,  water,  etc 32  Edge 14,812 


100.00 


Heated  to  1200°  to  1400°  F.  its  color  changed  to  red  and  its 
strength  was  entirely  gone. 

Gillmore  found  the  crushing  strength  of  sandstones-  to  vary 
from  4025  to  17,725  Ibs.  per  square  inch. 

Colorado  Sandstone. 

In  Boulder  County,  Colorado,  are  several  deposits  of  sandstone 
that  furnish  stone  for  building  and  street-construction  purposes. 
The  products  have  been  used  principally  in  Denver  «and  Omaha, 
but  are  scattered  about  in  many  smaller  towns  in  both  States. 

The  stone  varies  in  color  from  a  gray  to  a  light  red  according 
to  the  composition  of  the  iron  compounds. 

It  is  generally  found  in  layers  from  j  inch  to  several  feet  in 
thickness  at  an  angle  of  about  30°  with  the  horizon.  It  splits 
easily  along  the  cleavage  planes,  and  breaks  readily  at  right  angles, 
so  that  it  is  formed  into  flagging,  curbstones,  and  paving-blocks 
without  difficulty.  It  is  hard  and  tough  and  wears  well  and 
smoothly  in  a  pavement.  Its  grain  and  texture  are  such  that,  al- 
though smooth,  it  is  never  slippery,  and,  when  laid  on  an  un- 
yielding base,  after  a  little  wear  it  forms  a  smooth  and  pleasing 
pavement,  very  similar  to  one  made  of  Medina  stone. 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


The  following  table  shows  the  results  of  tests  of  Colorado  sand- 
stone, made  for  the  State  Capitol  and  given  in '"  U.  S.  Mineral  Re- 
sources" for  1886: 

TABLE  No.  3. 


Locality. 

Color. 

Position. 

Crushing 
Strength 
per  sq.  in. 

Specific 
Gravity. 

St.  Trains  

Light  red 

j  Bed 

11505 

2.393 

1  Edere 

17187 

Fort  Collins  

Gray 

j  Bed 

11707 

2.252 

/  Edge 

10784 

Do 

Light  red 

jBed 

12740 

2.432 

(  Edge 

17487 

gtout  

Dark  crrav 

j  Bed 

10514 

2.263 

"j  Edge 

12585 

Grayish  white 

(  Bed 

18573 

2.379 

i  Edge 

17261 

ANALYSIS   OF   COLORADO   SANDSTONE. 

Stout. 
Per  cent. 

Silica  95.50 

Iron  and  alumina 0.78 

Calcium  oxide 0.88 

Magnesia 1.45 

Carbonic  acid  and  water 1.18 


99.79 


Buck  Horn. 
Per  cent. 

96.45 
1.90 
1.06 
0.64 
0.00 

100.05 


Limestone. 


Although  limestone  as  well  as  sandstone  is  a  sedimentary  rock, 
it  differs  from  it  very  much  in  its  formation. 

Water  flowing  down  from  a  rough  mountainous  country  carries 
with  it  a  large  amount  of  matter  both  in  solution  and  suspension. 
As  the  stream  reaches  any  large  body  of  still  water  its  velocity  gradu- 
ally decreases  and  that  portion  in  suspension  is  deposited,  the 
coarser  and  heavier  near  the  shore  and  the  finer  farther  out. 

Calcareous  matter  as  a  rule,  being  soft,  is  generally  fine  and  is 
borne  from  a  distance  and  finally  deposited  as  silt.  All  waters 
flowing  as  above  contain  a  considerable  quantity  of  lime  in  solu- 
tion which,  being  in  part  precipitated,  serves  to  consolidate  the  silt. 
From  this  same  source  certain  marine  animals  derive  their  supply 


f 


UNIVERSITY 


STONE.  35 


for  their  shells.  Upon  the  death  and  decomposition  of  the  animal 
life  the  shells  and  corals  axe  left  and,  breaking  up,  in  time  form 
calcareous  banks  which  later  on  become  beds  of  limestones  of  more 
or  less  fragmental  nature. 

The  theory  of  the  formation  of  oolitic  varieties  is  somewhat 
different.  It  is  supposed  that  certain  fragments  of  calcareous  mat- 
ter have  been  deposited  upon  the  bottom  of  some  ancient  sea,  and 
that  they  were  kept  in  motion  by  the  action  of  the  waves  or  some 
other  force,  preventing  their  solidification.  If,  then,  the  lime  in 
solution  should  from  any  cause  become  too  much  for  the  absorption 
of  the  marine  animals,  it  would  be  precipitated,  and  would  form 
around  the  fragments,  which,  being  in  motion,  would  become  ap- 
proximately spherical  in  shape.  But  as  the  precipitation  continues 
the  interstices  become  filled  and  beds  of  solid  stone  are  formed 
having  the  appearance  peculiar  to  this  variety. 

Both  of  the  above  formations  are  generally  in  well-defined  beds 
nearly  level  when  not  disturbed  by  any  subsequent  force.  When, 
however,  as  often  happens,  the  strata  are  found  at  all  angles  with 
the  horizontal,  they  have  been  acted  upon  by  some  of  the  forces  so 
frequent  during  the  formation  of  the  earth's  crust. 

In  the  course  of  time  some  of  these  beds  may  be  broken  up 
into  fragments  comparatively  small  and  after  having  settled  into 
a  permanent  position  and  again  consolidated  by  the  further  de- 
posits of  lime  or  iron  oxides  in  the  interstices  of  the  fragments.  It 
is  thus  that  the  metamorphic  limestones  are  formed. 

Limestones  differ  greatly  in  structure  from  the  variety  highly 
charged  with  fossils  to  the  hard  compact  rocks  denser  and  heavier 
than  granite. 

They  also  vary  in  color  according  to  the  iron  and  carbonaceous 
compounds  that  may  be  present. 

As  calcite  crystallizes  so  readily,  few  limestones  are  entirely 
amorphous,  but  range  gradually  from  the  amorphic  to  the  holo- 
crystalline.  Few  limestones  are  pure  calcium  carbonate.  Impuri- 
ties are  easily  mixed  with  the  lime  during  the  formation.  Mag- 
nesium is  often  found  in  considerable  quantities,  when  the  variety 
is  called  magnesian.  When  this  amount  exceeds  45.65  per  cent 
the  stone  takes  the  name  of  dolomite.  Dolomite  has  a  specific 
gravity  of  about  2.9. 


36          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Silica  and  clay  are  often  found  in  composition,  and  when  they 
exist  in  quantities  exceeding  10  per  cent  the  stone  is  said  to  be  hy- 
draulic. That  is,  upon  being  burned  and  ground  it  can  be  made 
into  mortar  that  will  harden  under  water,  a  property  not  belonging 
to  ordinary  limestones.  A  specimen  of  this  variety  from  Kondout, 
N.  Y.,  analyzed  according  to  Dana: 

Per  cent. 

Carbonic  acid 34.20 

Lime    25.50 

Magnesia    12.35 

Silica   15.37 

Alumina 9.13 

Sesquioxide  of  iron 2.25 


98.80 

Marble  is  a  name  given  to  certain  crystalline  limestones  that 
are  of  such  a  character  as  to  be  capable  of  receiving  a  high  polish 
and  so  become  of  value  for  building  purposes.  Certain  dolomites 
are  also  called  marble. 

Bedford  Oolitic  Limestone. 

This  stone  is  properly  a  calcareous  sandstone  or  freestone,  dif- 
fering from  sandstone  in  having  its  grains  composed  of  carbonate 
of  lime  instead  of  quartz,  and  in  the  grains  being  small  fossils  in- 
stead of  sediment  transported  by  water  from  some  former  rock- 
mass.  It  differs  from  other  limestone  in  its  granular  texture  and 
freestone  grain. 

It  occurs  in  a  bed  varying  from  25  to  100  feet  in  thickness. 
The  greater  portion  of  it  is  free  from  laminations  or  bedding 
seams.  In  almost  every  quarry  or  natural  exposure  there  is  at  least 
one  system  of  vertical  joints,  but  they  are  rarely  so  numerous  as 
to  prevent  the  occurrence  of  the  stone  in  large  dimensions. 

It  is  a  granular  stone,  and  both  the  grains  and  uniting  cement 
are  carbonate  of  lime.  In  the  common  sandstones  the  grains  are 
hard  and  approximately  angular;  in  this  stone  the  grains  are  al- 
ways soft  and  either  round  or  rounded.  In  the  silicious  sandstones 
the  grains  are  harder  than  the  cement,  in  the  Bedford  the  cement 
is  harder  than  the  grains.  These  grains  are  nearly  all  small  fossil 
forms,  but  when  they  are  large,  that  portion  of  the  stone  containing 
them  is  thrown  away  and  not  used,  the  finest-grained  being  much 


STONE. 


37 


the  better  if  it  is  uniform  in  texture  and  color.  The  original  color 
was  blue,  but  it  is  sometimes  found  buff  and  even  a  mixed  blue  and 
buff,  according  to  the  chemical  changes  in  the  iron  compound. 

It  is  found  in  several  counties  of  Indiana  and  extends  across 
the  Ohio  River  into  the  State  of  Kentucky.  It  takes  its  name  from 
the  village  of  Bedford,  Indiana. 

A  series  of  tests  to  determine  its  compressive  strength  gave  an 
average  of  7000  pounds  per  square  inch  with  a  maximum  of  13,200 
pounds. 

Experiments  on  1-inch  cubes  were  also  made  to  ascertain  its 
fire-resisting  qualities.  Heated  to  1000°  F.  and  plunged  into  cold 
water  the  samples  were  not  affected.  Heated  to  1200°  and  treated 
in  the  same  manner  the  cubes  crumbled  slightly  along  the  lower 
edges.  Heated  to  1500°  and  cooled  in  the  air  the  cubes  retained 
their  form,  but  were  calcined  in  a  marked  degree. 

The  principal  use  of  this  stone  is  for  building  purposes.  It  is 
easily  cut  when  taken  from  the  quarry,  but  hardens  upon  expo- 
sure to  the  atmosphere.  It  is  also  used  in  street  construction  for 
curbing  and  flagging,  being  easily  sawed  to  any  required  dimen- 
sions. 

TABLE  No.  4. 

ANALYSIS   OF  BEDFORD   STONE   FROM   DIFFERENT  LOCALITIES. 


.Quarry. 

Crushing 
Strength. 

Specific 
Gravity. 

Calcium 
Carbonate. 

if 

1 

si 

•CT3 

jl 

Iron  Oxide  and 
Alumina. 

1 

Bedford   Ind  

5600 

2  47 

98  27 

0  84 

0  64 

0  15 

99  90 

Hunter  Valley  

4100 

98.11 

0  92 

0  86 

0  16 

100  05 

Romona  

9100 

2.48 

97.90 

0.65 

1.26 

0  18 

99  99 

Twin  Creek  ...     . 

9900 

2  51 

98  16 

0  97 

0  76 

0  15 

100  04 

Trenton  Limestone. 

This  deposit  takes  its  name  from  a  township  in  Oneida  County, 
New  York.  It  is  one  of  the  most  important  in  this  country,  ex- 
tending from  Maine  on  the  east  to  the  Eocky  Mountains  on  the 
west  and  from  Hudson's  Bay  to  Alabama.  By  its  decay  it  has 
formed  soils  of  great  fertility.  That  of  the  celebrated  Blue  Grass 
region  of  Kentucky  is  a  direct  product  of  the  decomposition  of  this 
stone. 


38 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


In  its  original  locality  it  is  dark  blue  in  color,  verging  to  black 
and  lying  in  even  beds  which  are  sometimes  separated  by  layers 
of  black  shale.  It  contains  well-preserved  specimens  of  the  Lower 
Silurian  Age.  It  changes  in  color  and  composition  as  it  extends 
in  different  directions,  but  is  easily  followed  by  its  distinctive 
features. 

It  is  used  for  building  purposes,  burned  into  lime,  and  broken 
up  for  road-building,  according  to  the  wants  of  any  particular  sec- 
tion where  it  is  located. 

Table  No.  5  gives  the  result  of  several  analyses  of  this  stone. 
TABLE  No.  5. 


'> 

ill 

| 

2 

0 

S 

if 

ii« 

| 

_o 

•o  o> 

O 

c  « 

c  o 

c      / 

,& 

3 

^r; 

r:  o3 

i 

a  ^i-3 

ojS 

III 

o 

a 

"5 

o 

| 

|i 

02 

0 

^ 

di 

OD 

cc 

c» 

Average  of  7  specimens  non-mag- 

2.698 

90.976 

1.828 

2.155 

.489 

.453 

.470 

.265 

3.794 

Average   of   11    specimens   mag- 
nesian        ....          

2.681 

64.323 

23.541 

3.410 

.414 

.632 

.590 

.278 

6.078 

Table  No.  6  shows  the  analyses  of  different  limestones  and  their 
resulting  limes. 

TABLE  No.  6 


Bridgeport, 
Penn. 

Longview, 
Ala. 

Barton, 
Ga. 

Hanover, 
Penn. 

Calcium  carbonate.  .  . 
Magnesium  carbonate 
Oxide  of  iron  and  alu- 
mina    
Silica  and  silicates  .  .  . 

Stone. 

Lime.; 

Stone. 

Lime. 

Stone. 

Lime. 

Stone. 

Lime. 

55.70 
41.97 

0.72 
1.58 

1.35 
2.95 

99.16 
0.75 

Trace 
0.15 

1.50 
0.56 

0.26 
0.37 

56.02 
38.43 

1.50 
1.94 



83.12 
8.23 



1.236 
7.252 
1.622 

0.03 
0.63 

o.oa 

0.53 

Calcium  oxide  
Magnesium  oxide  
Potassium    carbonate 



58.33 
37.37 



97.30 



34.070 
55.736 



92.00 
3.55 
4.23 

7.43 

Total     

99.97 

100.00 

100.06 

99.99 

97.89 

99.916 

99.44 

100.34 

STONE. 


Table  No.  7  gives  the  composition  of  limestone  from  different 
localities. 

TABLE  No.  7. 


„  3 
§  = 

i 

u 

4J 
S 

V 

2 

S 

r*    ^ 

a 

"3  . 

H 

^ 

M 

Cg 

5  s 

—  S 

T*    * 

s 

o 

M 

•S 

C- 

£ 

E 

^3 

s 

«  0> 

Q 

E"£ 

i-? 

£•0 

«•- 

3 

"Cb 

CT3 

|2 

^o 

y 

«3 

•S3 

0 

1" 

I 

| 

5s 

« 
5 

S 

Howard  Co    Md  

77.82 

3  19 

5.15 

13  60 

0.24 

91  538 

944 

1  3:14 

O     OQ 

2  854 

Hannibal   Mo         

98.80 

.02 

0  40 

06 

Ulster  Co.,  New  York  

97.00 

0.40 

2.60 

95.30 

1.25 

3  62 

Nat  ural  Bridge,  N.Y.*.... 
Vernon    N  J 

52  45 

43.25 

0.24 
1.34 

0.24 
2.28 

5  45t 

6  35J 

22.43 

29.48 

47.73 

Columbus,  Ohio  

93.21 

4  70 

1.74 

West  Winfleld,  Penn  

95.10 

1.12 

1.00 

2.78 

Lannon,  Wis  

52.29 

42.27 

1.68 

3.96 







Calumet  Co    Wis  

55  09 

43  96 

.36 

.59 

98  29 

462 

167 

533 

578 

*  Dolomite.       t  Alumina.       $  Phosphorus. 
In  five  samples  of  Missouri  limestone  the  calcium  carbonate  averaged  99.2*. 

Limestones  tested  by  General  Gillmore  for  crushing  strength 
varied  from  3450  to  25,000  Ibs.  per  square  inch. 


CHAPTEE   III. 

ASPHALT. 

ASPHALT  or  bitumen  under  some  name  has  been  in  use  for  many 
ages.  The  terms  have  been  used  so  much  synonymously  as  well 
as  interchangeably  that  it  is  often  difficult  to  tell  just  what  varie- 
ties are  referred  to.  The  practice  is  still  kept  up  to  a  certain  ex- 
tent, some  authorities  speaking  of  asphalt,  others  of  asphaltum,  and 
some  of  both,  while  all  are  practically  referring  to  the  same  sub- 
stance. Some  specifications  have  mentioned  pure  asphaltum.  It 
would  be  extremely  difficult  at  the  present  time  to  establish  legally 
what  pure  asphaltum  is.  As  one  writer  has  said,  asphalt  is  an 
occurrence  and  not  a  distinct  substance. 

In  America  natural  bituminous  pavements  are  called  asphalt; 
in  France,  asphalte  comprime;  in  Germany,  S  tamp  f- Asphaltum; 
and  in  England,  asphalte. 

In  the  English  translation  of  the  Bible  it  is  stated  that  Noah 
was  told  to  pitch  the  ark  with  pitch;  and  in  another  chapter  in 
Genesis,  that  when  the  tower  of  Babel  was  built  slime  was  used 
for  mortar;  and  in  Exodus,  that  the  ark  of  bulrushes  in  which 
Moses  was  found  was  daubed  with  slime  and  pitch.  In  each  of  these 
cases  the  Latin  version  renders  the  words  "  slime  "  and  "  pitch  " 
as  "  bitumen  "  except  in  the  case  of  Moses'  ark,  both  words  being 
used  in  the  same  sentence;  "  pitch  "  is  rendered  pice,  the  ablative 
form  of  pix. 

In  the  Greek  version  these  words  are  all  rendered  acrcfiaTiTos, 
or  from  the  same  root  except  as  above  in  Exodus,  where 
ao-<J)a\.T07iicr(rrj  is  used.  This  latter  word  is  said  by  Liddell  and 
Scott  to  be  the  same  as  ^rzcr<T«(J0ar/lroS',which  means  a  compound 
of  asphalt  and  pitch.  Eiddell  and  White  define  bitumen  as  "A 
kind  of  asphaltum,  Jew's  pitch,  or  fossil  tar,"  and  add  that  it  was 

40 


ASPHALT.  41 

frequently  found  in  Palestine  and  Babylon.  Bitumen,  they  say, 
is  from  the  Hebrew  word  chemar,  and  orcr0arAro£  from  two 
Hebrew  words  meaning  "  mud." 

Liddell  and  Scott  also  say  that  the  belief  that  acrcpaXros 
is  derived  from  <70orAAa?is  erroneous. 

It  is  also  stated  in  profane  history  that  bitumen  was  used  in 
building  the  hanging  gardens  of  Babylon,  and  in  other  works  of 
masonry  construction  in  both  Babylon  and  Xineveh.  It  was  also 
used  in  making  cisterns  water-tight.  Tradition  says  that  this  pitch 
came  from  the  springs  of  Oyen  Hit  on  the  Euphrates. 

In  the  light  of  all  this  it  is  safe  to  say  that  some  forms  of 
bitumen  have  been  known  to,  and  used  by,  the  human  race  from 
very  early  periods.  In  some  sections  of  Europe  examples  of 
masonry  constructed  with  a  bituminous  cement  are  still  extant. 

Before  proceeding  to  an  extended  discussion  of  bitumen  in  any 
of  its  forms,  it  will  be  fitting  to  examine  the  various  definitions  that 
have  been  given  to  it  by  different  writers  and  students. 

Whatever  form  is  studied,  it  must  be  understood  that  bitumen 
is  the  essential  base  of  all,  and  that  will  be  considered  first.  Prof. 
S.  F.  Peckham,  formerly  of  the  University  of  Michigan,  and  who 
has  been  engaged  more  or  less  in  the  study  of  this  subject  since 
1865,  defines  bitumen  as  "  That  large  class  of  substances  occurring 
in  nature  as  minerals  and  consisting  chiefly  of  mixtures  of  com- 
pounds of  carbon  and  hydrogen,  with  nitrogen,  sulphur,  and 
oxygen  as  more  rare  constituents." 

Prof.  Sad  tier  says:  "The  word  bitumen  in  mineralogy  is  ap- 
plied to  hydrocarbon  mixtures  of  mineral  occurrence,  whether  solid, 
liquid,  or  gaseous." 

Clifford  Richardson,  formerly  Inspector  of  Asphalt  and 
Cements,  says:  "  The  natural  bitumen  which  is  known  as  asphalt 
is  composed,  as  far  as  we  have  been  able  to  learn,  of  unsaturated 
hydrocarbons  and  their  sulphur  derivatives  with  a  small  amount  of 
nitrogenous  constituents." 

Mr.  A.  W.  Dow,  at  present  Inspector  of  Asphalt  and  Cements, 
"Washington,  defines  bitumen  as  "  Any  and  all  hydrocarbons, 
whether  natural  or  artificial,  soluble  in  carbon  bisulphide." 

Leon  Malo,  an  eminent  French  writer  on  the  subject,  says  that 
in  1861  he  made  the  following  definition,  and  in  1897  he  can  do  no 


42  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

better  than  to  reiterate  it:  "  Bitumen  or  pitch,  the  materials  which 
impregnate  asphalt." 

As  defined  by  Dana,  "  Asphaltum  or  mineral  pitch  is  a  mixture 
of  different  hydrocarbons,  part  of  which  are  oxygenated." 

Richardson:  "Asphalt  may  therefore  be  defined  as  any  hard 
bitumen,  composed  of  unsaturated  hydrocarbons  and  their  deriva- 
tives, which  melts  upon  the  application  of  heat  to  a  viscous  liquid." 

Mr.  Dow  defines  both  asphaltum  and  asphalt: 

"  Asphaltum — A  natural  bitumen,  all  or  a  portion  of  which  is 
soluble  in  petroleum  naphtha,  and  in  most  cases  found  associated 
with  various  mineral  and  organic  substances." 

"  Asphalt — Any  and  all  natural  deposits  containing  asphaltum." 

An  unknown  writer:  "  Asphalt  is  a  compact  bitumen,  a  product 
of  the  decomposition  of  vegetable  matter,  consisting  mainly  of 
hydrocarbons  with  variable  quantities  of  oxygen  and  nitrogen." 

Leon  Malo:  "Asphalt,  calcareous -rock  impregnated  naturally 
by  bitumen  or  pitch."  * 

Prof.  Peckham:  "  The  words  natural  .gas,  naphtha,  petroleum, 
maltha,  asphaltum,  and  asphalt  are  not  names  of  things,  but  words 
which  indicate  accidents  of  occurrence  to  which  any  species  of 
bitumen  may  be  subject.  When  a  true  system  of  classification  of 
the  species  and  subspecies  under  bitumen  has  been  reached,  it  will 
be  found  that  a  species  may  occur  in  nature  in  any  or  all  of  the 
several  conditions  from  natural  gas  to  asphalt.  A  true  system, 
therefore,  must  name  and  classify  the  bitumens  themselves." 

These  different  definitions  from  these  different  investigators 
have  been  given  in  order  that  it  may  be  clearly  seen  in  what  respect 
the  people  who  are  studying  the  questions  to-day,  and  who  are 
probably  as  conversant  with  the  subjects  as  any  one  in  the  world, 
differ,  and  in  what  they  agree. 

The  great  difference  between  the  definitions  of  Leon  Malo  and 
the  American  writers  will  be  noticed.  According  to  him,  nothing 
but  what  is  known  in  this  country  as  "  rock  asphalt "  can  be  con- 
sidered under  that  name.  As  a  matter  of  fact,  all  asphalt  pave- 
ments laid  in  the  American  manner  are  called  artificial  pavements 
in  Europe.  That  is,  the  paving  material  must  be  formed  by  nature 
in  order  to  constitute  a  real  asphalt  pavement. 

The  American   definitions  are  very  much   alike  in   essential 


ASPHALT.  43 

points,  except  that  Mr.  Dow  uses  and  defines  "  asphaltum  "  and 
"  asphalt."  There  does  not  seem  to  be  any  necessity  for  considering 
an  intermediate  substance  between  bitumen  and  asphalt.  Neither 
does  there  seem  to  be  any  reason  why  some  writers  should  use 
<e  asphaltum  "  and  others  "  asphalt "  when  referring  to  exactly  the 
same  substance.  Asphalt,  being  the  shorter  and  the  more  nearly 
English  in  form,  will  be  adopted  for  use  in  this  work. 

A  careful  study  of  the  foregoing  definitions  would  suggest  a 
combination  of  some  of  them  by  which  the  ideas  of  the  writers 
might  be  incorporated  together,  with  a  result  that  might  be  more 
•satisfactory  than  any  one  alone. 

Prof.  Peckham's  definition  of  bitumen  is  scientific  and  exact, 
but  it  is  long  and  inconvenient.  It  does  not  seem  necessary  in  a 
definition  to  give  all  the  constituents  of  a  substance  nor  all  its  prop- 
erties, but  sufficient  only  to  render  it  easily  recognized.  It  would 
seem,  therefore,  that  by  transposing  Prof.  Sadtler's  words  and 
adding  some  of  Mr.  Richardson's,  a  definition  of  bitumen  might  be 
reached  that  would  not  be  too  long  and  would  satisfy  all  scientific 
requirements. 

This  is  suggested,  then:  "  Bitumen — Any  unsaturated  hydro- 
carbon mixture  of  mineral  occurrence,  whether  solid,  liquid,  or 
gaseous/' 

In  connection  with  the  above  may  be  quoted  a  statement  of 
Prof.  Peckham's:  "  Bitumens  from  natural  gas  to  asphaltum  in- 
clude compounds  and  mixtures  of  compounds  belonging  to  all  the 
known  series  of  hydrocarbons.7' 

He  also  divides  bitumens  into  the  following:  solid,  asphaltum; 
semi-fluid,  maltha;  fluid,  petroleum;  volatile,  naphtha;  gaseous, 
natural  gas. 

In  speaking  further  of  maltha  he  says:  "  Some  of  these,  fluid 
varieties  of  bitumen  both  in  Europe  and  America  pass  by  insensible 
degrees  and  by  natural  causes  into  maltha,  which  is  a  semi-fluid 
TISCOUS  form  of  bitumen,  known  as  mineral  tar  and  just  as  clearly 
to  be  distinguished  in  consistence  from  petroleum  as  common  tar 
is  to  be  distinguished  from  olive-oil.  I  have  found  the  change  by 
which  California  petroleum  is  converted  into  maltha  to  be  due  to 
two  causes,  viz.,  evaporation  and  indirect  oxidation.  When  air, 
ozone,  or  chlorine  is  passed  through  the  paraffine  petroleums,  they 


44          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

are  condensed  by  evaporation  to  a  residue  resembling  vaseline. 
When  California  petroleums  are  treated  in  the  same  manner,  they 
are  condensed  by  decomposition  into,  first,  maltha  and  then 
asphaltums." 

It  may  be  of  interest  to  state  here  that  natural  gas  has  been 
declared  to  be  a  bitumen  by  the  United  States  Supreme  Court. 

The  Buffalo  Gas  and  Fuel  Co.  brought  natural  gas  from  Canada 
by  means  of  pipes  laid  under  the  Niagara  River.  The  customs 
officials  sought  to  collect  an  import  duty  upon  it.  The  case  went 
to  the  Supreme  Court,  and  in  a  decision  rendered  January  3,  1899, 
natural  gas  was  declared  to  be  a  crude  bitumen  and  entitled  to  be 
admitted  free  of  duty. 

Admitting  the  foregoing  definition  for  bitumen,  the  one  that 
follows,  and  it  would  seem  naturally,  is:  Asphalt — Any  hard  natu- 
ral bitumen,  or  any  deposit  containing  such  bitumen  in  appreciable 
quantities. 

Any  asphalt  which  has  any  distinctive  feature  about  it  can  be 
qualified  by  the  characteristic  adjective,  such  as  rock  asphalt  when 
the  deposit  is  rock  impregnated  with  bitumen,  thus  doing  away  with 
a  multiplicity  of  terms  and  making  each  one  self-explanatory. 

In  considering  the  origin  of  asphalt,  or  rather  of  the  bitumen 
composing  it,  attention  must  be  given  to  the  petroleums,  as  the 
different  authorities  generally  agree  as  to  the  direct  production  of 
asphalt  from  petroleum. 

Prof.  Wurtz  says  that  asphalt  is  probably  formed  by  the  gradual 
oxidation  of  petroleum:oil.  Dana  states  that  petroleum  passes  by 
insensible  gradations  into  pitt  asphalt  or  maltha  (viscid  bitumen), 
and  the  latter  as  insensibly  into  asphalt  or  solid  bitumen. 

Prof.  Peckham  on  visiting  California  in  1865  witnessed  all  the 
natural  phenomena  attending  the  passage  of  petroleum  through 
maltha  into  asphalt  upon  a  very  extended  scale. 

A  German  writer  gives  the  following  as  his  theory: 

"  In  the  oldest  of  the  stratified  rocks  are  found  remains  of  the 
eozoon,  the  animal  of  the  dawn  of  creation,  a  member  of  the  in- 
fusoria. This  division  of  nature  is  made  up  of  diatoms  and  pro- 
tozoa, The  diatoms  have  two  shells.  These  shells  are  composed  of 
silica  and  pure  quartz;  inside  the  shell  is  the  living  thing  which 
consists  of  a  single  cell  of  protoplasm.  Throughout  this  plasm- 


1  ASPHALT.  45 

mass  are  scattered  globules  of  fat  or  oils.  When  the  plasm  leaves 
its  shell,  the  latter,  being  composed  of  quartz,  sinks  to  the  bottom 
and  is  preserved. 

"  The  protozoa  members  of  the  infusoria  are  less  regular  in 
shape  than  the  diatoms.  They  consist  of  a  protoplasm-cell  and 
generally  have  a  shell  of  quartz  or  calcium  carbonate.  The  pro- 
toplasm-matter of  these  animals  also  contains  oil-globules  scattered 
throughout  the  mass.  The  great  chalk  formations  of  the  earth  are 
made  entirely  of  the  remains  of  some  of  the  protozoa.  The  ooze  at 
present  being  deposited  on  the  floor  of  the  Atlantic  is  composed 
entirely  of  protozoa,  the  greater  part  being  carbonate  of  lime,  about 
ten  per  cent  being  similar  to  the  infusorial  earth  found  in  the 
island  of  Barbadoes. 

"  In  the  West  Indies  and  in  California  wherever  asphalt  is 
found,  there  also  exist  large  deposits  of  marine  infusorial  earth. 
What  is  more  natural  than  to  suppose  that  the  vast  quantities  of 
diatoms  and  protozoa  have  left  their  bony  skeletons  as  infusorial 
earth,  have  yielded  up  their  organic  matter,  and  especially  their 
contained  oil-globules,  to  the  formation  of  asphalt? 

"  The  chemical  elements  contained  in  protoplasm  are  identical 
with  those  composing  asphalt,  although  they  do  not  exist  in  the 
same  proportions. 

"  Recently  two  substances  have  been  derived  from  asphalt  that 
have  been  obtained  hitherto  only  by  the  distillation  of  animal  re- 
mains. And  by  the  heating  of  fish-oils  under  pressure,  chemists 
have  been  able  to  produce  the  members  of  the  paraffine  series." 

Leon  Malo  admits  that  at  some  indeterminate  epoch  consider- 
able masses  of  vegetables  or  animals  buried  in  sedimentary  beds, 
and  heated  either  directly  by  the  central  heat  or  by  the  invasion 
of  volcanic  currents,  have  in  an  immense  distillation  given  birth 
to  all  the  bitumens.  It  is  certain  that  this  gigantic  action  was 
exercised  in  a  very  varied  manner,  according  to  place,  temperature, 
pressure,  the  nature  of  the  neighboring  rocks,  the  epoch  of  its 
operation,  and  the  original  material,  the  product  differing  in  form, 
appearance,  composition,  and  properties.  But  the  mode  of  forma- 
tion has  been  the  same  throughout,  and  the  resulting  bodies  con- 
tain an  identical  principle,  the  bituminous  principle,  which  does 
not  resemble  any  other  body  and  for  which  it  is  not  to  be  mistaken. 


46  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Peckham,  reviewing  the  above,  says  that  this  view  of  the  origin 
of  bitumen,  while  very  near  the  truth,  is  founded  upon  conjecture 
rather  than  proof,  and  has  led  to  an  assumed  identity  among  all 
forms  of  bitumen  that  has  enthroned  error  and  discouraged  re- 
search, with  results  that  have  been  altogether  unfortunate. 

DoljJhus  Torrey,  a  chemist  who  has  given  many  years  to  ex- 
aminations of  and  experiments  with  bitumens  in  their  various 
forms,  writes  that  there  is  -a  tendency  to  assign  the  origin  of  petro- 
leum, ozokonite,  or  mineral  wax,  and  asphalt  to  an  animal  origin 
more  widely  entertained  than  ever  before.  It  is  difficult  to  imagine 
any  other  origin  for  these  materials  as  found  in  many  large  deposits, 
and  in  all  deposits  which  are  productive  on  a  commercial  scale  the 
conditions  are  consistent  with  the  theory  of  animal  origin.  The 
theory  of  distillation  from  coal  and  other  vegetable  deposits  to 
account  for  petroleum  is  beset  with  difficulties,  while  the  condi- 
tions of  such  deposits  admit  our  assuming  the  probable  existence 
of  animal  life  whenever  vegetable  growth  was  possible. 

The  mineral  theories  announced  to  account  for  the  generation 
of  petroleum  appear  to  be  without  any  basis  of  probability. 

A  correspondent  of  the  Engineering  and  Mining  Journal  quotes 
from  an  article  in  the  Austrian  Zeitschrift  fur  Berg-  und  Hutten- 
wesen  as  follows:  "  It  has  been  urged  that  the  absence  of  nitrogen 
in  petroleum  must  be  fatal  to  the  theory  of  its  animal  origin,  be- 
cause an  oil  produced  from  animal  substances  could  not  fail  to  be 
nitrogenous.  One  answer  to  this  argument  was  furnished  when 
Dr.  Engler  actually  produced  from  blubber  and  other  animal  fats 
an  artificial  petroleum  free  from  nitrogen,  as  might  have  been  ex- 
pected, since  the  fats  are  non-nitrogenous.  And  Engler  declares 
that  the  absence  of  nitrogen  in  natural  petroleum  is  a  necessary 
result  of  its  production  from  animal  remains,  because  the  nitrog- 
enous flesh  decays  rapidly  and  assumes  soluble  forms,  so  that  it 
would  be  removed  before  the  fat,  which  is  peculiarly  stable,  began 
to  be  transformed  by  the  slower  process  of  dry  distillation." 

This  proposition  was  confirmed  by  Dr.  M.  Albrecht,  who  treated 
several  thousand  mussels  and  fishes  in  this  way  and  found  that  the 
ammonia  and  nitrogenous  bases  incidentally  produced  were  easily 
removed  by  reason  of  their  extreme  solubility  in  water. 

Prof.  Peckham's  examination  of  the  petroleum  of  California, 


1  ASPHALT.  47 

Texas,  West  Virginia,  and  Ohio  showed  the  presence  of  nitrogen 
and  led  to  the  general  acceptance,  for  these  oils,  of  the  theory  of 
an  animal  origin  which  was  still  denied  for  many  of  the  non-nitrog- 
enous Pennsylvania  oils. 

Farther  on,  in  speaking  of  the  report  made  by  Gumbel  upon  the 
samples  taken  from  the  sea-bottom  during  the  voyage  of  the 
Gazelle,  the  above  correspondent  continues:  "  In  samples  taken 
from  depths  of  500  metres  and  over,  fine  globules  of  fat  were  found 
similar  in  character  to  adipocene  sometimes  found  in  ancient  graves, 
or  the  fat  still  remaining  in  fossil  bones.  Director  Gumbel  recog- 
nizes the  possible  significance  of  this  discovery  in  connection  with 
the  origin  of  petroleum." 

Prof.  \Vm.  C.  Day  of  the  U.  S.  Geological  Survey  details  an 
experiment  in  relation  to  this  subject.  He  says  introductory: 
"  As  a  result  of  considerable  experimental  work  in  the  la.<t  few 
years  with  asphalt  from  a  variety  of  sources  in  the  United  States, 
together  with  a  study  of  literature  pertaining  to  the  origin  of 
bitumens  from  both  the  geological  and  the  chemical  standpoint,  I 
became  impressed  with  the  belief  that  the  solid  and  also  some  of 
the  higher  boiling  liquid  bitumens  have  been  formed  in  the  earth 
b}r  the  distillation  of  mixed  animal  and  vegetable  material  together 
with  steam  at  high  temperatures,  but  at  pressures  that  may  or  may 
not  have  been  high." 

Mr.  Day  placed  a  number  of  fresh  herring,  a  quantity  of  pine 
^awdust,  and  a  number  of  pieces  of  fat  pine  wood  in  a  cylindrical 
iron  retort  and  distilled  it.  Of  the  result  he  says  that,  on  cooling, 
the  contents  of  the  bulb  became  a  black  brittle  solid,  showing  a 
very  pronounced  resemblance  to  gilsonite  in  every  way,  with  the 
following  properties:  black,  glistening  color,  becoming  brown  on 
pulverizing  and  slightly  darker  than  gilsonite;  fracture  conchoidal, 
entirely  soluble  in  carbon  bisulphide;  90.6  per  cent  soluble  in 
ether,  66.3  per  cent  in  alcohol,  and  61.1  per  cent  in  petroleum 
ether.  As  the  distilling  bulb  cracked  before  it  had  been  intended 
to  stop  the  distillation,  another  trial  similar  to  the  above  was  made, 
except  that  the  heating  was  continued  longer.  Of  the  second  result 
he  says  that  he  obtained  a  substance  so  much  like  gilsonite  that  it 
was  difficult  to  tell  one  from  the  other. 

A  combustion  of  the  first  samples  gave  carbon  87.5  and  hy- 


4:8  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

drogen  7.7  <per  cent;  and  of  the  second  88.9  per  cent  carbon  and 
6.7  hydrogen.  The  figures  for  Utah  gilsonite  are  88.3  per  cent  for 
carbon  and  9.9  per  cent  for  hydrogen. 

He  continues  by  declaring  'that  the  distillation  of  fish  alone, 
without  the  wood  mixture,  gave  nothing  like  gilsonite,  and  the  dis- 
tillation products  were  totally  unlike  in  every  way  from  those  ob- 
tained by  the  mixing  of  fish  and  wood. 

In  1860  Messrs.  Wall  and  Sawkins  made  a  report  on  the  geology 
of  the  island  of  Trinidad,  in  which  they  describe  at  length  the 
pitch  lake  and  the  attending  phenomena.  They  call  the  deposit 
"  asphaltum,"  and  ascribe  to  it  a  vegetable  origin.  They  contend 
that  the  only  substances  that  contain  sufficient  carbon  and  hy- 
drogen for  the  formation  of  asphalt  are  animal  and  vegetable  re- 
mains. The  latter  are  particularly  abundant  at  La  Brea,  where 
most  of  the  asphaltic  beds  have  been  originally  carbonaceous  and 
lignitic  shales.  They  found  what  they  considered  to  be  specimens 
showing  every  stage  of  transformation  from  the  first  -deposit  to  the 
total  obliteration  of  organic  structure,  when  nothing  but  the  ex- 
ternal form  of  the  wood  was  left.  After  detailing  some  other 
observations  they  say:  "  These  circumstances  conduct  us  to  the 
proposition  that  the  bituminous  substances  of  La  Brea,  whether 
fluid  or  solid,  have  been  fornred  from  vegetable  material  by  direct 
conversion  at  the  ordinary  temperature/' 

The  change  is  thus  described:  "  The  first  department  of  the 
process  consists  in  the  formation  of  a  black  oily  substance  similar 
to  what  arises  in  a  liquid  form  at  the  surface,  and  hasi  been  termed 
asphaltic  oil.  This  may  not  be  invariably  the  case,  but  has  been 
frequently  noticed  particularly  with  respect  to  ligneous  masses  as 
distinguished  from  leaves  and  fragments.  There  is  a  constant  en- 
deavor on  the  part  of  this  fluid  to  escape  from  the  material  in 
which  it  was  formed.  Some  specimens  of  wood  in  the  earliest 
stages  of  conversion  continued  to  discharge  oil  for  several  months 
after  being  placed  in  the  museum  of  the  Survey  at  Port  of  Spain." 

They  also  found  pieces  of  wood  that  had  accidentally  fallen 
into  the  asphalt  and  been  partially  transformed.  Also  specimens 
that  they  thought  were  derived  from  leaves  that  had  been, blown 
upon  the  lake. 

They  say  that  while  the  process  of  transformation  over  the 


ASPHALT.  49 


La  Brea  district  has  generally  ceased,  there  is  sufficient  activity 
to  indicate  clearly  the  source  of  material  and  the  manner  of  de- 
velopment. 

In  commenting  on  the  above  theory,  Richardson  says  that  ex- 
cavations made  at  the  pitch  lake  since  the  report  of  Wall  and  Saw- 
kins  do  not  confirm  their  deductions:  that,  on  the  contrary,  the 
deposits  show  no  signs  of  conversion  of  vegetable  matter  into  bitu- 
men, and  that  their  origin  has  been  largely  a  mere  infiltration  of 
the  soil  of  the  bitumen  already  formed  and  which  has  subsequently 
changed  in  its  chemical  nature  under  the  existing  conditions. 

A  large  proportion  of  the  bitumen  has  undoubtedly  come  from 
the  lake,  and  another  portion  has  been  forced  up  from  below  in 
a  quite  liquid  state  in  much  the  same  way  as  is  seen  at  the  soft 
spot  in  the  lake.-  He  does  not  believe,  therefore,  that  the  bitumin- 
ous substances  at  La  Brea  have  been  formed  from  vegetable  material 
by  direct  conversion  at  ordinary  temperatures. 

He  states  that  asphalt  is  being  formed  now,  not  as  a  primary 
but  as  a  secondary  product,  resulting  from  the  transformation  of 
lighter  forms  of  bitumen,  maltha,  or  even  thinner  oils  into  harder 
bitumen  by  condensation  and  polymerization — a  reaction  in  which 
sulphur  seems  to  take  an  important  part. 

Peckham  declares  that  when  he  visited  the  lake  he  looked  in 
vain  for  any  wood  in  process  of  formation  into  asphalt;  that  he 
inquired  of  many  people  connected  with  mining  the  pitch,  and 
could  find  no  one  who  had  ever  .seen  any.  On  the  contrary,  one 
man  told  him  that  the  wood  never  decayed  in  the  pitch;  another, 
that  if  it  went  in  rotten  it  came  out  rotten. 

Prof.  Moissan  attributes  the  origin  of  petroleum  to  metallic 
carbides,  because  carbides  produce  different  'hydrocarbons  on  con- 
tact with  water:  carbide  of  aluminum  producing  methane;  car- 
bide of  calcium,  acetylene;  and  carbide  of  uranium,  a  mixture  of 
hydrogen,  methane,  and  ethylene. 

Mendele Jeff's  theory  is  that,  after  admitting  the  existence  of 
metallic  carbides,  it  is  easy  to  find  an  explanation  not  only  for  the 
origin  of  petroleum,  but  also  for  the  manner  of  its  appearance  in 
the  places  where  the  terrestrial  strata  at  the  time  of  their  eleva- 
tion .into  mountain-chains  ought  to  be  filled  with  crevices  to  their 
centre.  These  crevices  have  admitted  water  to  the  metallic  car- 


50  STREET  PAVEMENTS  AND  PAVING  MATERIALS.      . 

bides.  The  action  of  the  water  upon  these  carbides  at  an  elevated 
temperature  and  under  a  high  pressure  has  generated  metallic 
oxides  and  saturated  hydrocarbons  which,  being  transposed  by 
aqueous  vapor,  have  reached  those  strata  where  they  would  easily 
condense  and  impregnate  beds  of  sandstone. 

Prof.  Wurtz  in  his  "  Chemical  Technology "  says  that,  ac- 
cording to1  some,  the  formation  of  petroleum  is  intimately  connected 
with  the  occurrence  of  hydrocarbons  met  with  (according  to  the 
observations  of  Dumas,  H.  Eoe,  and  Bunsen)  in  compressed  condi- 
tion in  many  rock-salt  deposits,  from  which  they  are  set  free  either 
in  the  state  of  gas  or  as  naphtha  when  the  salt  comes  into  contact 
with  the  water  or  is  broken  up. 

Prof.  Peckham  in  a  Eeport  on  Petroleum  for  the  Tenth  Census 
states  that  there  are  three  general  theories  as  to  the  origin  of 
bitumen: 

"  1.  Bitumen  indigenous  to  the  rock  in  which  it  is  found. 

"  2.  Bitumen  a  result  of  chemical  action  in  natural  products. 

"  3.  Bitumen  the  result  of  chemical  reaction  between  purely 
mineral  or  inorganic  materials." 

After* an  exhaustive  examination  of  the  subject  he  concludes: 
"  I  am  convinced  that  all  bitumens  in  their  present  condition  have 
originally  been  derived  from  animal  or  vegetable  remains,  but  that 
the  manner  of  their  derivation  has  not  been  uniform." 

He  thinks  the  bitumens  of  California  and  Texas  are  undoubtedly 
indigenous  to  the  shales  from  which  they  issue. 

In  Ventura  County  the  petroleum  is  primarily  held  in  strata 
of  shale,  from  which  it  exudes  as  petroleum  or  maltha,  according 
as  the  shales  have  been  brought  into  contact  with  the  atmosphere. 
The  asphalt  is  produced  by  further  exposure  after  the  bitumen  has 
reached  the  surface. 

He  continues:  "  The  exceedingly  unstable  character  of  petro- 
leums, considered  in  connection  with  the  amount  of  nitrogen  that 
they  contain  and  the  vast  accumulation  of  animal  remains  in  the 
strata  from  which  they  issue,  together  with  the  fact  that  the  fish- 
oils  soon  become  filled  with  the  larvae  of  insects  to  such  an  extent 
that  the  pools  of  petroleum  become  pools  of  maggots,  all  lend 
support  to  the  theory  that  the  oils  are  of  animal  origin/' 

After  considering  the  petroleums  of  New  York,  Pennsylvania, 


ASPHALT.  51 

Ohio,  and  West  Virginia,  lie  concludes  that  they  are  distillates  of 
vegetable  origin. 

A  careful  study  of  these  theories  will  demonstrate  how  much 
and  how  materially  some  of  them  differ  from  each  other,  as  well  as 
how  satisfied  the  authors  are  that  they  are  right  in  their  con- 
jectures. 

It  will  be  noticed,  too,  that  all  the  American  writers,  men  who 
have  investigated  the  subject  in  recent  years  from  a  practical  as 
well  as  a  scientific  standpoint,  seem  to  agree  that  bitumen  must 
have  had  its  origin  in  some  organic  matter,  either  animal  or 
vegetable. 

The  opinion  of  Prof.  Peckham,  a  man  who  has  been  studying 
the  question  for  so  many  years,  who  has  visited  so  many  of  the 
asphalt  fields,  and  has  spent  so  much  time  in  patient  work  in  the 
laboratory,  must  carry  great  weight. 

Bitumen  belongs  to  that  great  group  of  hydrocarbons  about 
which  it  is  very  difficult  to  give  positive  results.  Chemists  feel 
as  if  this  group  is  a  fertile  field  for  experiment,  but  hesitate  when 
asked  to  give  positive  information  about  any  one  of  them.  Until 
the  last  few  years,  their  researches  had  mainly  to  be  labors  of  love 
for  the  good  of  science  as  far  as  asphalt  is  concerned. 

In  1837  Boussingault  made  some  exhaustive  analyses  and  ex- 
aminations of  Bechelbronn  asphalt,  and  his  conclusions  were 
accepted  for  many  years.  He  found  this  particular  variety  to  be 
composed  of: 

Per  cent. 

Carbon   85.90 

Hydrogen    11.25 

Oxygen  2.85 

100.00 

He  separated  the  bitumen  into  two  parts  which  he  called 
petrolene  and  asphaltene.  Petrolene  is  a  thick  oily  fluid,  while 
asphaltene  is  hard  and  brittle.  The  former  is  the  cementitious 
part  of  the  bitumen  and  serves  as  a  solvent  to  the  hard  asphaltene, 
making  the  whole  mass  serviceable  for  pavements.  The  relative 
proportions  of  these  two  constituents  in  any  bitumen  are  important. 
If  it  contain  too  much  petrolene,  the  resulting  mixture  will  be 


52  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

soft  and  sticky;  while  if  the  asphaltene  be  in  excess,  the  mixture, 
while  perhaps  good  when  first  laid,  or  in  warm  weather,  would  soon 
disintegrate  and  crack  badly  when  the  temperature  became  cold. 

While  bitumen  is  considered  to  be  composed  of  these  two  sub- 
stances, it  must  be  distinctly  understood  that  they  are  not  definite 
chemical  compounds,  but  occurrences  in,  or  properties  of,  the  bitu- 
men. Boussingault  did  assign  a  chemical  formula  to  them,  C20H32 
for  petrolene  and  C20H3203  for  asphaltene;  that  is,  in  the  latter 
case  the  petrolene  has  become  oxidized.  Thomson,  however,  varied 
the  above,  making  petrolene  C10H8  and  asphaltene  C10H803;  and 
other  chemists  have  arrived  at  still  different  results. 

Chemists  differ  also  as  to  the  methods  and  solvents  to  be  used 
in  extracting  the  bitumen  from  asphalt,  and  their  determinations 
differ  according  to  these  means  and  methods.  The  amount  of 
bitumen  in  a  crude  asphalt  is  not  important  as  far  as  the  character 
of  the  pavement  is  concerned,  but  commercially  it  is  highly  so, 
as  upon  the  quantity  depends  the  amount  of  paving  mixture  that 
can  be  obtained  from  a  given  amount  of  the  crude  material. 

In  making  his  analysis,  Clifford  Eichardson  dissolves  the 
material  dried  in  vacuo  in  successive  portions  of  carbon  bisulphide 
and  naphtha,  passing  the  decanted  solvents  through  a  Gooch  cruci- 
ble with  heavy  asbestos  felt.  The  filtrate  in  the  case  of  the  bi- 
sulphide extract  is  allowed  to  settle  for  24  hours,  again  decanted, 
and  any  fine  sediment  that  passes  the  filter  brought  upon  it.  The 
losses  represent  the  bitumen  soluble  in  the  two  solvents.  He  adds: 
"  Great  care  is  essential  in  these  determinations,  especially  that 
the  solvents  be  perfectly  dry.  On  this  account  bisulphide  is  much 
more  suitable  for  use  than  oil  of  turpentine  or  chloroform,  as  it  i's 
not  nearly  so  hygroscopic,  although  it  is  not  quite  as  complete  a 
solvent  unless  used  hot." 

Prof.  Sadtler  uses  acetone  to  extract  the  petrolene,  and  chloro- 
form for  the  asphaltene,  giving  as  a  reason  that  they  can  be  had 
perfectly  pure  and  are  not  alterable,  so  that  they  possess  distinct 
advantages  over  petroleum  ether,  or  carbon  bisulphide. 

Miss  Laura  A.  Linton,  who  has  made  some  very  valuable 
analyses,  recommends  digesting  the  asphalt  with  petroleum  ether, 
decanting  the  liquid  upon  a  filter,  as  well  as  the  undissolved  bitumen. 
The  filter  and  contents  are  then  treated  with  boiling  turpentine. 


ASPHALT.  53 

This  treatment  is  continued  until  the  filtrate  becomes  colorless, 
when  chloroform  is  taken  to  extract  the  asphaltene. 

Prof.  Endemann's  method:  The  refined  asphalt  is  treated  with 
chloroform,  and  the  residue  collected  on  a  weighed  filter  and 
treated  in  the  manner  as  described  by  Miss  Linton.  The  chloro- 
form solution  is  then  distilled  from  a  weighed  flask,  and  the  residue 
in  the  flask  dried  at  120°  for  half  an  hour.  A  portion  of  the 
residue  is  then  placed  in  a  porcelain  boat  and  treated  in  a  cur- 
rent of  C02  for  12  hours  at  a  temperature  of  250°.  To  avoid 
volatilization,  the  asphalt  should  be  spread  over  as  large  a  surface 
as  possible.  Loss,  petrolene;  residue,  asphaltene  and  ash.  An 
elementary  analysis  can  be  made  of  the  latter  if  desired. 

In  nearly  all  of  the  above  methods  it  is  considered  that  carbon 
bisulphide  or  chloroform  will  dissolve  all  of  the  bitumen,  and  that 
of  this  bitumen  the  portion  soluble  in  petroleum  ether  is  petrolene 
and  the  remainder  asphaltene.  Or  if  the  material  be  treated  first 
with  petroleum  ether,  the  amount  soluble  is  petrolene  and  the 
further  amount  obtained  from  chloroform  treatment  is  asphaltene. 

Prof.  Endemann  works,  it  will  be  seen,  upon  very  different  lines 
from  those  previously  described,  and  he  contends  that  the  above 
method  is  wrong,  as  it  produces  a  result  that  is  far  from  correct 
as  regarding  the  relative  proportions  of  petrolene  and  asphaltene. 
He  contends  that  by  the  use  of  petroleum  ether  a  large  amount  of 
asphaltene  is  dissolved  and  is  consequently  called  asphaltene.  On 
comparing  the  two  methods  he  says: 

"  I  had  to  admit,  and  do  admit,  that  the  analysis  as  carried  out 
"by  the  later  methods  suffices  to  make  identity  or  nonentity  of  two 
samples  probable  or  highy  probable.  It  is  also  adapted  to  watch 
the  supply  of  a  single  mine  or  the  refining  of  asphalt  from  the 
same  source;  but  it  does  not  admit  of  basing  any  conclusions  upon 
the  results  if  we  work  on  asphalts  from  different  sources." 

He  analyzes  two  samples  of  Trinidad  and  one  of  Mexican  asphalt 
"by  both  processes,  and  shows  by  the  result  that  what  has  generally 
been  called  petrolene  really  contains  only  about  43  per  cent  of 
petrolene,  the  reason  being  that  a  large  amount  of  asphaltene  has 
"been  dissolved  by  petroleum  ether. 

From  these  analyses  he  derives  the  results  shown  in  the  follow- 
ing table  under  "  New  Method." 


54:  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

TABLE  No.  8. 

PETROLKNK.  ASPHALTENK. 

Old  New  Old  New 

Method.  Method.          Method.          Method. 

Trinidad  Lake 31.86  13.70  28.12  46.28 

Trinidad  Land 24.97  10.74  33.37  47.70 

Mexican 87.12  37.45  10.19  59.85 

Commenting  upon  the  results,  he  says:  "  I  believe  no  one 
accustomed  to  the  figures  generally  reported  for  these  excellent 
asphalts  would  recognize  them  in  this  shape." 

Continuing  his  investigation  still  further,  he  deduces  C13H18O 
or  a  multiple  for  asphaltene,  and  for  petrolene  CnH2n,  formulae 
which  vary  considerably  from  those  of  Boussingault  or  Thomson. 

In  explanation  of  these  he  states  that  the  formula  for  asphaltene 
has  been  verified  by  direct  analysis,  but  that  of  petrolene  has  been 
deduced  from  a  mixture  and  may  require  verification;  also  that 
petrolene  includes  a  series  of  compounds,  while  asphaltene  appears 
as  a  single  body,  differing  from  the  substance  called  asphaltene  by 
Boussingault  by  containing  less  oxygen. 

To  quote  further:  "  I  have  been  asked  whether  it  would  not  be 
possible  to  recalculate  the  many  analyses  especially  of  crude  asphalts 
made  during  the  last  few  years  to  avoid  the  loss  of  so  much  labor. 
To  this  I  have  to  answer  that  it  is  not  possible,  for  the  reason  that 
the  higher  petrolenes,  when  dissolved  in  petroleum  ether,  exert  a 
greater  dissolving  influence  upon  asphaltene  than  the  lower.  How- 
ever, as  regards  refined  paving  asphalts,  an  approximation  is  pos- 
sible and  may  be  reached  by  dividing  the  petrolene  found  by  the 
old-time  analysis  by  3J.  This  will  give  us  real  petrolene.  The 
difference  between  this  figure  and  the  original  is  to  be  added  to  the 
asphaltene." 

When  it  is  considered  upon  what  different  methods  different 
chemists  base  their  results,  it  will  be  readily  understood  how  neces- 
sary it  is  that  whenever  an  analysis  of  any  asphalt  is  given  out  there 
should  be  added  to  it  a  statement  giving  solvents  and  methods  used 
in  the  analysis;  also  that  asphalts  cannot  be  compared  by  their 
chemical  analyses  unless  the  same  methods  have  been  pursued  in 
each  case. 

When  chemists  disagree,  the  engineer  cannot  step  in  and  decide 
the  question,  but  must  do  the  best  he  can  under  the  existing  cir- 


ASPHALT.  55 

cumstances  and  await  the  results  of  further  investigations.  The 
commercial  value  of  asphalt  is  now  so  great  that  the  subject  will 
not  be  allowed  to  rest,  but  will  be  continually  studied  until  it  is 
completely  understood.  The  engineer  is  not  interested  from  a 
scientific  but  a  practical  standpoint.  He  does  not  care  what  par- 
ticular solvent  is  used;  and  if  an  asphalt  containing  a  certain  per- 
centage of  bitumen  soluble  in  carbon  bisulphide  or  chloroform,  and 
a  certain  portion  of  that  bitumen  soluble  in  petroleum  ether  or 
naphtha,  will  make  a  good  pavement  when  properly  mixed  and  laid, 
that  is  enough  for  him.  He  is  willing  to  leave  exact  determinations 
to  be  made  by  the  chemist.  Unfortunately  that  stage  has  not  yet 
been  reached. 

If  carbon  bisulphide  be  used  as  a  solvent  for  the  total  bitumen, 
not  only  its  temperature  but  its  specific  gravity  must  be  specified. 
And  if  a  new  asphalt  is  -being  examined  with  a  new  supply  of 
solvents, it  will  be  safer  to  make  a  complete  analysis  of  a  well-known 
asphalt  and  compare  these  results  with  those  obtained  from  the 
new  specimen  when  the  same  materials  were  used.  In  this  wa^ 
reliable  comparisons  ought  to  be  made. 

The  chemist  should  not  confine  himself  to  strictly  chemical  re- 
search. Asphalt  in  pavements  is  called  upon  to  resist  sudden  and 
extreme  changes  of  temperature  ranging  from  30°  below  zero  to 
140°  above,  as  many  of  our  cities  have  extremes  of  temperature  of 
this  amount.  The  effect  upon  the  samples  should  be  carefully 
noted  at  every  30°.  These  results  will  serve  for  comparison  when 
the  specimen  under  examination  is  given  the  same  treatment,  and 
in  this  way  the  probable  relative  values  of  the  two  asphalts  de- 
termined as  far  as  this  one  property  is  concerned.  Pursuing  the 
same  method  in  relation  to  its  absolute  hardness,  viscosity,  etc.,  the 
worth  of  the  new  paving  material  for  paving  purposes  can  be 
pretty  accurately  determined. 

It  is  doubtful,  however,  in  the  present  stage  of  asphalt  knowl- 
edge if  any  chemist  would  be  willing  to  give  a  positive  opinion  upon 
the  real  value  of  any  sample  from  any  examination,  whether  chemi- 
cal, mechanical,  or  both.  It  seems  to  be  pretty  generally  accepted 
that  the  only  sure  way  of  determining  the  merits  of  a  new  asphalt 
is  by  giving  it  a  trial.  This  requires  time  and  careful  experiments, 
for  a  treatment  giving  good  results  with  a  bitumen  from  one  lo- 


56  STREET  PAVEMENTS  AND   PAVING  MATERIALS. 

cality  may  be  very  unsuccessful  with  another  although  the  chemi- 
cal properties  may  be  very  similar.  The  mechanical  examination, 
if  properly  carried  out,  will  throw  much  light  upon  this  part  of  the 
investigations. 

For  some  time  chemists  had  considerable  difficulty  in  distin- 
guishing natural  from  artificial  bitumen.  They  belong  to  the  same 
hydrocarbon  group  'and  act  similarly  under  solvents.  Five  years 
ago  an  expert  chemist  frankly  admitted  that  chemically  he  could 
not  tell  if  asphalt  was  adulterated  with  coal-tar,  but  it  could  be 
easily  detected  by  its  odor,  and  no  appreciable  adulteration  could 
have  taken  place  without  its  discovery  if  submitted  to  an  expert. 

In  Thorpe's  Dictionary  of  Applied  Chemistry  the  following 
mode  of  procedure  is  laid  down:  "  Native  asphalt  can  be  distin- 
guished from  artificial  asphalt  by  extracting  with  carbon  bisulphide, 
filtering,  evaporating  to  dryness,  and  heating  the  residue  until  it 
can  be  ground  to  a  dry  powder;  0.1  gram  is  treated  with  5  c.c.  of 
fuming  sulphuric  acid  for  24  hours  and  is  then  mixed  with  con- 
tinuous stirring  with  10  c.c.  of  water.  If  pitch  or  coal-tar  be  pres- 
ent, the  solution  will  be  of  a  dark-brown  or  blackish  tint;  if  not, 
the  solution  will  be  of  a  light  yellowish  color."  This  method  has 
been  tried  and  found  to  be  satisfactory  when  the  amount  of  tar 
present  in  the  asphalt  was  as  small  as  7  per  cent,  and  without  doubt 
would  have  been  equally  so  had  the  quantity  been  even  less. 

Asphalt  has  been  found  in  different  forms  widely  scattered 
over  the  earth's  surface. 

In  the  Eastern  Hemisphere  the  principal  localities  are  Austria, 
France,  Germany,  Eussia,  Sicily,  Switzerland,  and  Syria;  in  the 
Western,  Cuba,  Mexico,  Trinidad,  the  United  States,  and  Vene- 
zuela. 

Of  the  above  France,  Germany,  Sicily,  and  Switzerland  furnish 
the  rock  asphalt  used  in  the  pavements  of  Europe,  while  the 
material  for  the  American  pavements  comes  from  Trinidad, 
Venezuela,  and  the  United  States. 

In  the  latter  country  asphalt  occurs  in  California,  Colorado, 
Indian  Territory,  Kentucky,  Montana,  Texas,  and  Utah,  although 
all  these  deposits  have  not  yet  been  used  for  pavements. 


1  ASPHALT.  57 

Trinidad  Asphalt. 

By  far  the  most  celebrated,  if  not  wonderful,  deposit  of  asphalt 
is  that  located  upon  the  island  of  Trinidad.  This  island  is  situated 
off  the  coast  of  Venezuela,  between  10°  and  11°  north  latitude  and 
in  61°  west  longitude.  The  principal  cities  are  on  the  west  coast, 
and  the  asphalt  deposit  is  about  40  miles  south  of  Port  of  Spain, 
the  chief  city,  and  adjoining  the  village  of  La  Brea,  the  Spanish 
word  for  pitch.  The  houses  of  the  village  are  built  upon  the 
asphalt,  and  on  account  of  its  motion  it  is  not  uncommon  for  a 
building  that  was  erected  on  its  proper  lot  to  project  years  after- 
ward upon  that  of  its  neighbor. 

Approaching  La  Brea  as  it  was  in  1892,  one  saw  asphalt  piled 
about  on  various  parts  of  the  shore  awaiting  shipment.  The  pieces 
ranged  from  the  size  of  a  cocoanut  to  something  over  a  cubic  foot, 
and  when  any  amount  was  left  in  the  sun  for  several  days  it  gradu- 
ally melted  and  became  once  more  an  amorphous  mass,  requiring 
to  be  broken  up  before  being  handled. 

The  lake,  as  the  Trinidad  deposit  is  generally  called,  is  about 
a  mile  from  the  shore  and  at  an  elevation  of  13&J  feet  above  the 
sea-level.  The  slope  is  gradual  and  very  regular.  The  lake  itself 
is  the  property  of  the  Crown  and  has  been  leased  to  certain  parties 
for  a  term  of  years,  who  alone  have  the  right  to  remove  any  material 
from  it.  The  village  lots,  however,  and  the  land  between  the  shore 
and  the  lake  contain  asphalt,  and  in  1892  a  great  quantity  of  it  was 
being  mined  from  these  exterior  localities.  Much  has  been  said 
by  interested  parties  as  to  the  origin  of  this  external  material. 
"Whether  it  had  its  origin  inside  and  is  an  overflow  from  the  lake, 
or  whether  its  appearance  is  due  to  the  same  causes  as  that  of  the 
lake,  as  well  as  the  relative  value  of  the  two  kinds,  will  not  be  dis- 
cussed here. 

Advancing  up  the  slope  to  the  main  deposit,  the  appearance  is 
much  like  the  approach  to  a  stone-quarry,  asphalt  taking  the  place 
of  the  stone,  and  tropical  vegetation  being  seen  instead  of  the  hardy 
growths  that  cover  our  rocky  hills. 

In  some  places  the  pitch  is  at  the  surface,  at  others  it  is  several 
feet  below,  with  bushes  and  quite  large  trees  growing  upon  it. 
The  earth  is  removed  rnrl  the  asphalt  dug  with  common  picks  to 


58  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

depths  of  four  or  five  feet.  Water  soon  accumulates  in  these  holes 
from  the  adjacent  pitch.  At  the  time  of  the  visit  spoken  of  there 
was  nothing  to  determine  the  thickness  of  this  outside  deposit,  as 
plenty  of  material  could  be  obtained  without  excavating  to  any 
inconvenient  depth.  Upon  gaining  the  top  of  the  slope,  and  at  the 
same  time  the  edge  of  the  lake,  one  experiences,  at  first  glance,  a 
tinge  of  disappointment,  as  nothing  is  seen  to  suggest  a  real  lake. 
Instead  the  appearance  is  that  of  a  morass  with  growths  of  grass, 
bushes,  and  small  trees  scattered  over  it.  A  large  portion  of  the 
surface,  however,  is  open,  divided  into  irregular  areas  much  like 
the  back  of  an  immense  turtle,  water  being  found  in  the  dividing 
depressions. 

The  entire  area  has  been  accurately  surveyed  and  determined, 
and  it  is  approximately  circular  in  shape,  containing  about '114 
acres.  Excepting  at  one  place  near  the  centre,  the  surface  is 
hard,  so  that  a  horse  and  loaded  cart  can  be  easily  driven  over  it. 
Near  the  centre  it  is  so  soft  that  a  person  walking  into  it  will  sink 
nearly  up  to  his  knees.  This  material  can  be  gathered  up  in  the 
hand,  and  on  being  squeezed  water  runs  freely  from  it.  The  ad- 
hesiveness is  such  that  the  fingers  are  not  materially  soiled  in  the 
handling.  This  central  mass  is  warm,  not  hot,  and  seems  to  be  con- 
stantly disturbed.  Sulphuretted  hydrogen  gas  bubbles  forth  in 
small  quantities. 

At  the  time  of  the  author's  visit  the  material  was  being  mined 
from  the  surface  by  hand  with  ordinary  tools  and  loaded  into  carts 
and  drawn  to  the  shore  by  mules,  and  from  there  taken  to  the  ships 
in  the  roadstead  in  lighters. 

The  pitch  was  excavated  for  a  depth  of  a  few  feet  as  might  be 
convenient,  and  the  hole  left  while  the  work  was  pursued  else- 
where. On  account  of  the  pressure  below,  or  the  action  of  the  en- 
tire mass,  these  holes  are  filled  in  less  than  48  hours,  and  in  a  few 
days  the  surface  is  as  hard  as  ever.  There  is  some  testimony  that 
the  excavations  outside  of  the  lake  proper  will  fill  up  in  a  similar 
manner  in  a  longer  time,  but  there  was  no  visible  evidence  of  it  at 
that  time. 

In  1894  the  concessionnaires  built  an  iron  pier  far  enough  out 
into  the  gulf  to  allow  steamers  to  come  alongside.  A  railroad- 
track  was  built  upon  the  surface  of  the  lake  and  so  constructed  that 


ASPHALT.  59 

cars  could  be  run  by  cable  around  the  entire  lake  and,  when  loaded 
at  any  desired  point,  drawn  to  the  initial  station,  where  the  body 
of  the  car  is  lifted  from  the  trucks  and  conveyed  by  an  overhead 
cable  down  to  the  water,  out  over  the  iron  pier,  and  the  material 
dumped  into  the  hold  of  the  vessel  waiting  to  receive  it.  As  illus- 
trating some  of  the  properties  of  this  asphalt,  it  might  be  said  that 
when  this  plant  was  first  operated  asphalt  was  the  only  fuel  used  for 
some  time;  also  that  the  oil  used  for  street-lighting  in  Port  of  Spain 
was  manufactured  from  this  material. 

*  In  189-1  borings  were  made  to  determine  the  depth  of  the 
pitch.  At  the  centre  a  depth  of  135  feet  was  reached,  still  in 
pitch,  but  the  movement  of  the  mass  prevented  any  further  distance 
being  attained.  This  depth  was  within  3£  feet  of  sea-level.  On 
the  north  side  of  the  lake,  about  100  feet  from  the  edge  and  1000 
feet  from  the  centre,  pitch  of  a  uniform  character  was  found  for 
a  depth  of  75  feet.  At  80  feet  a  few  feet  of  sand  was  discovered, 
followed  by  more  pitch  to  a  depth  of  90  feet.  From  there  on  to 
150  feet  the  boring  was  in  sand  mixed  with  asphalt. 

Similar  borings  made  outside  of  the  lake  showed  the  latter 
formation  near  the  surface,  and  on  the  south  side,  about  1300  feet 
from  the  centre,  a  hard  asphaltic  sandstone  was  encountered  at  a 
depth 'of  about  80  feet.  From  these  different  observations  it  'has 
been  estimated  that  the  asphalt  has  been  deposited  in  an  old  crater 
some  2300  feet  in  diameter  and  over  135  feet  deep,  and  amounts  in 
quantity  to  about  9,000,000  tons. 

From  levels  run  in  1893  the  centre  of  the  lake  was  found  to  be 
at  an  elevation  of  138.5  feet  above  sea-level  and  about  one  foot 
higher  than  the  portion  1000  feet  from  the  centre  in  an  approxi- 
mately northwesterly  direction,  from  which  point  the  surface  rose 
six  inches  at  the  edge.  The  highest  point  is  at  the  south  side  with 
an  elevation  of  141.4,  and  the  lowest  toward  the  west  and  north  side, 
where  it  is  about  138  feet  above  sea-level. 

The  surface  is  evidently  lower  than  in  former  years,  a  natural 
condition  when  it  is  remembered  that  more  than  a  million  tons 
of  asphalt  have  been  removed  from  it.  From  the  actual  amount 
of  the  depression  and  the  amount  it  should  have  been  lowered  by 
the  output  of  the  last  thirty  years,  it  has  been  figured  by  Mr. 

*  This  description  of  the  Pitch  Lake  is  from  Richardson's  "  On  the  Nature 
and  Origin  of  Asphalt." 


60 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


Kichardson  that  there  must  have  been  an  influx  of  new  material 
of  from  18,000  to  20,000  tons  per  year  between  1893  and  1896. 

The  movement  of  the  surface  was  shown  by  stakes  set  for  run- 
ning levels.  These  were  driven  every  hundred  feet  for  a  distance 
of  600  feet  from  the  centre.  In  three  weeks'  time  the  centre  stake 
had  moved  20.6  feet  to  the  right  and  12.2  feet  ahead.  The  one 
showing  the  least  motion  to  the  right  was  at  station  4,  being  0.2- 
foot  and  2.4  feet  ahead,  while  at  station  3  the  stake  had  moved  1.7 
feet  but  had  kept  its  distance.  The  other  stakes  varied  between, 
these  limits  and  that  at  the  centre. 

A  mass  of  pitch  containing  vegetation  was  found  in  1894  to 
have  moved  5.5  feet  laterally  and  23  feet  in  line  from  the  observed 
position  in  1893. 

TABLE  No.  9. 

ANALYSES  OF   SAMPLES   OF  PITCH  TAKEN  AT   DIFFERENT  DISTANCES   FROM 

THE  CENTRE. 


Bitumen 

Feet  from 
Centre. 

Soluble  in 
Carbon 

Mineral 
Matter. 

Organic  Matter 
not  Soluble. 

Soluble  in 
Naphtha. 

Total  Bitumen. 
Soluble. 

Bisulphide. 

200 

55.02 

35.41 

9.57 

31.83 

57.85 

400 

54.99 

35.40 

9.61 

31.63 

57.55 

600 

54.84 

35.49 

9.67 

31.85 

58.26 

800 

54.66 

35.56 

9.78 

31.67 

57.97 

1000 

54.78 

35.44 

9.78 

31.58 

57.64 

1100 

54.62 

35.45 

9.93 

31.77 

57.51 

Average 

54.92 

35.46 

9.72 

31.72 

57.79 

1400 

53.86 

36.38 

9.76 

30.52 

56.66 

The  above  results  were  obtained  by  using  hot  carbon  bisulphide 
and  having  each  sample  thoroughly  dried  before  being  treated. 

The  asphalt,  as  above  described,  is  in  a  crude  state  and  must 
be  refined  before  being  suitable  for  pavements.  This  work  is  gen- 
erally done  in  this  country  at  the  most  convenient  seaport.  The 
object  of  the  refining  is  to  evaporate  the  water,  drive  off  the 
more  volatile  oils,  and  remove  the  coarser  material.  The  process 
consists  in  heating  the  asphalt  in  large  iron  retorts  to  a  tempera- 
ture  of  about  400°  F.  for  some  five  or  six  days,  according  to  condi- 
tions. The  foreign  matter  is  allowed  to  settle  to  the  bottom,  and 
the  remainder  drawn  off  into  barrels  or  boxes  for  shipment.  The 


ASPHALT.  61 

sediment  is  then  removed  from  the  stills  and  used  for  some  inferior 
purpose.  The  loss  in  refining  is  about  33  per  cent,  so  that  as  a 
rule  three  tons  of  the  crude  material  make  two  tons  of  the  re- 
fined. 

This  was  the  first  method  adopted.  But  as  a  large  portion  of 
the  foreign  matter  of  Trinidad  is  silicious  and,  if  taken  out,  will 
have  to  be  replaced  when  a  paving  mixture  is  prepared,  another 
process  has  been  in  use  during  the  last  few  years.  The  apparatus 
consists  of  an  iron  retort  sufficiently  large  to  contain  some  30  or 
40  tons  of  crude  material.  In  the  inside  is  a  continuous  iron  pipe 
arranged  in  gangs  somewhat  like  a  steam-radiator,  having  a  return 
pipe  to  take  the  condensed  water  back  to  the  boiler.  Another  set 
of  pipes,  called  the  live-steam  pipes,  has  a  direct  boiler  connection 
and  a  number  of  jets  inserted  in  it  at  the  bottom,  so  that  the 
material  in  the  retort  can  be  kept  hot  and  in  constant  agitation  by 
the  injection  of  hot  steam  through  these  pipes,  thus  insuring  a  com- 
plete and  even  mixture  as  well  as  more  rapid  evaporation.  The 
retort  being  filled,  steam  is  applied  and  the  material  heated  to  a 
temperature  of  about  300°  F.  After  this  treatment  has  been  ap- 
plied for  about  sixteen  hours,  the  water  is  evaporated  and  the 
asphalt  is  ready  for  use  or  shipment.  If  this  work  is  done  near 
the  mixing-plant,  the  flux  is  added  before  the  product  is  drawn  off 
and  the  asphaltic  cement  made  without  further  apparatus. 

This  method  is  called  the  drying  process,  rather  than  refining, 
as  the  only  change  is  the  evaporation  of  the  water. 

The  tariff  on  the  crude  being  less  than  on  the  refined  article, 
a  test  case  was  made  with  one  cargo,  and  the  final  determination  by 
the  courts  was  that  the  asphalt  treated  as  above  must  be  considered 
as  in  a  crude  state. 

The  average  of  Richardson's  analyses  previously  given  for  the 
dried  asphalt  is  bitumen  soluble  in  carbon  bisulphide  54.92  per  cent. 
Of  this  bitumen  70.12  per  cent  can  be  considered  petrolene  and 
29.78  per  cent  asphaltene.  Its  specific  gravity  is  about  1.38. 

California  Asphalt. 

In  the  State  of  California  bitumen  can  probably  be  found  in 
more  forms  and  more  localities  than  in  any  other  part  of  the  world. 


62  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

It  is  said  to  exist  there  in  all  the  intermediate  stages  between 
natural  gas  and  the  hard  asphalt. 

This  has  been  known  for  many  years.  It  was  originally  used 
by  the  natives  in  making  their  canoes  water-tight.  The  early 
Spanish  priests,  the  pioneers  of  civilization  in  that  region,  utilized 
it  in  constructing  floors,  roofs,  reservoirs,  and  conduits.  Later  on, 
the  Mexicans,  following  the  example  of  the  fathers,  continued  its 
use  in  practically  the  same  manner. 

But  this  was  all  local  and  was  carried  on  in  the  sections  near  or 
adjacent  to  the  deposits. 

It  was  not  till  1868  that  any  of  the  material  was  used  for  pave- 
ments, when  in  Santa  Cruz  an  old  wooden  pavement  was  covered 
with  bituminous  rock.  In  1876  more  of  it  was  used  as  an  original 
pavement,  and  since  that  time  its  use  has  been  extended  to  other 
cities  in  the  Pacific  States,  and  eventually  all  over  the  United 
States. 

The  forms  of  the  bitumen  adapted  to  pavements  are  maltha, 
asphalt,  and  bituminous  rock. 

Maltha  is  a  thick  viscous  bitumen,  flowing  sluggishly  at  ordinary 
temperatures,  but  very  freely  when  artificially  heated.  It  con- 
tains a  large  amount  of  bitumen,  of  which  a  considerable  percentage 
is  petrolene.  Its  office  is  to  serve  as  a  flux  for  the  asphalt.  Its 
petrolene  dissolves  the  asphaltene  of  the  harder  material  and  pro- 
duces a  mixture  suitable  for  paving  purposes,  the  amount  to  be 
used  varying  according  to  the  composition  of  the  ingredients  and 
the  results  desired.  Although  deposits  of  maltha  are  found  in 
many  sections,  the  one  of  most  commercial  value  is  situated  in 
Santa  Barbara  County,  about  13  miles  east  of  the  city  of  Santa 
Barbara  and  on  the  shore  of  the  Pacific  Ocean.  This  deposit  con- 
sists of  a  large  body  of  bituminized  sand  covering  an  area  of  about 
75  acres  for  a  depth  of  25  feet.  The  maltha  is  supposed  to  be  sup- 
plied from  a  stratum  of  bituminous  shale  upon  which  the  sand 
rests.  The  sand  is  covered  with  from  6  to  8  feet  of  surface  loam 
which  is  washed  off  into  the  sea  by  a  12-inch  stream  of  water  under 
pressure  supplied  by  steam-pumps.  A  thin  layer  of  clay  resting 
directly  upon  the  sand  is  then  removed  with  spades.  The  sand 
is  then  loaded  into  cars  with  hot  spades,  drawn  by  a  cable  up  an  in- 
clined way  to  the  refinery,  where  it  is  dumped  into  a  mixer  con- 


ASPHALT.  63 

sisting  of  a  steam-jacketed  cylinder  in  which  revolving  arms  break 
up  the  lumps.  The  material  then  falls  into  vats  of  boiling  water, 
the  maltha  floating,  and  the  sand,  sinking  to  the  bottom,  is  carried 
away  by  mechanical  means.  The  maltha  flows  from  the  surface  of 
the  water  through  a  spout  to  a  tank  whence  it  is  pumped  into  a 
storage  tank  of  higher  elevation.  From  there  it  runs  into  refining- 
kettles,  where  it  is  subjected  for  twenty-four  hours  to  a  heat  of 
100°  F.  at  first,  but  finishing  at  240°  F.  This  removes  all  aqueous 
vapors  and  volatile  oils,  when  the  material  is  ready  for  use.  The 
average  composition  of  this  product  is: 

Per  cent. 

Bitumen   98.26 

Mineral    matter 1.74 

The  bitumen  contains  94.13  per  cent  of  petrolene.  The  specific 
gravity  is  1.05. 

Twelve  miles  west  of  Santa  Barbara  is  located  a  deposit  of 
asphalt  proper.  This  covers  an  area  of  several  hundred  acres,  and 
the  material  is  mined  in  much  the  same  manner  as  coal.  The 
supply,  as  in  the  case  of  the  maltha,  seems  to  be  from  below.  As 
the  bottoms  of  the  mines  rise  the  asphalt  is  cut  off,  and  in  one 
drift  the  record  shows  that  a  total  of  52  feet  was  cut  from  the 
floor  in  one  year.  This  was  at  a  depth  of  about  125  feet  from  the 
surface.  The  deposit  extends  out  under  the  ocean,  and  from 
analyses  it  has  been  shown  to  be  the  same  as  that  extending  in- 
land. 

In  appearance  it  is  much  like  the  refined  Trinidad,  though  of 
less  specific  gravity.  At  a  temperature  of  70°  F.  it  is  hard  and 
brittle,  softening  at  105°  and  melting  at  248°.  The  crude  material 
contains  bitumen  59.15  per  cent,  organic  matter  1.10  per  cent,  and 
mineral  matter  39.75  per  cent.  Its  specific  gravity  is  1.25. 

It  is  refined  in  practically  the  same  manner  as  the  first  method 
described  for  Trinidad,  and  is  generally  brought  to  a  standard  of 
80  per  cent  bitumen  for  shipment. 

In  Santa  Barbara  County,  about  27  miles  from  and  2000  feet 
above  the  sea,  is  a  deposit  of  sand  bearing  bitumen  that  is  prac- 
tically of  unlimited  amount.  The  problem  has  been  to  convey  it 
to  the  coast  over  the  rough  and  sandy  country  intervening.  The 


64:          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

material  is  so  hard  that  it  requires  to  be  broken,  and  contains  about 
20  per  cent  bitumen. 

The  transportation  problem  has  been  solved  by  first  crushing 
the  sand  by  specially  devised  machinery,  and  conveying  it  to  a 
large  vat,  where  it  is  treated  with  a  form  of  gasolene  specially  pre- 
pared for  the  purpose  from  crude  petroleum.  The  gasolene  dis- 
solves the  bitumen  and,  carrying  it  in  solution,  overflows  the  vat,, 
runs  down  a  pipe-line  27  miles  to  the  shore,  where  it  is  distilled 
off  and  the  asphalt  reduced  to  the  desired  penetration  and  put  up 
in  barrels.  The  gasolene  is  then  pumped  back  to  the  mine  with 
very  little  loss  and  used  again.  The  sand  after  the  bitumen  has 
been  extracted  is  raised  by  means  of  a  screw,  being  sprayed  all  the 
time  with  gasolene  to  make  sure  that  it  is  entirely  free  from  bitu^ 
men,  and  deposited  outside  as  waste. 

The  entire  apparatus  and  process  are  protected  by  letters  patent. 
The  system  has  not  been  in  operation  a  sufficient  length  of  time  to 
demonstrate  what  will  be  its  ultimate  economy  and  capacity,  but 
long  enough  to  insure  its  complete  success. 

In  several  places  asphalt  is  produced  from  the  crude  petroleum 
oil. 

The  ordinary  method  is  to  pump  the  oil  and  accompanying 
water  from  the  wells  into  tanks  where  it  is  heated  by  steam-coils, 
to  a  temperature  of  about  220°  F.  This  lessens  the  weight  of  the 
oil,  which  rises,  allowing  the  greater  portion  of  the  water  to  be 
drawn  off  from  below.  The  remaining  moisture  is  then  evaporated 
by  increasing  the  heat. 

The  oil  is  then  conducted  to  the  refining-kettles,  where  it  is 
kept  heated  with  open  lid  till  it  will  stand  a  temperature  of  300°  F. 
without  foaming.  The  lid  is  then  screwed  down  and  the  tempera- 
ture gradually  increased  to  550°  F.  The  vapors  given  off  are 
withdrawn  by  suction.  The  process  is  continued,  the  heat  being 
increased  towards  the  end  to  700°  F.  till  a  sample  of  the  material 
poured  into  water  forms  a  hard  black  substance  that  bends  slightly 
and  breaks  under  moderate  pressure.  The  crude  oil  from  the 
Sunset  Oil  Works  in  Kern  County  yields  about  50  per  cent  distil- 
lates of  a  specific  gravity  of  20°  Beaume. 

The  average  of  100  barrels  of  mixed  crude  oils  from  Ventura 
County  was  as  follows: 


ASPHALT.  65 

Barrels. 

Gasoline,   76°    Beaum£ 3 

Benzine,    63°       "       4 

Kerosene,  45 3       "       15 

Heavy  kerosene,  38°  to  40°  Beauine 8 

Gas  distillate,.  28°  "       21 

Light  lubricating-oil,  26°          "       10 

Neutral  oil,  23°  "       12 

Heavy  neutral  oil,  21°  "       6 

Reduced-stock  lubricating-oil,  14°   Beauine" 5 

Asphalt,  crude 11 

Loss    5 

100 

In  the  western  part  of  Kern  County  there  are  important  de- 
posits of  asphalt.  In  some  localities  it  is  found  on  the  surface,  and 
in  others  as  veins  of  asphalt  in  the  mountain  rock.  The  surface 
material  was  used  at  first  with  good  results.  In  appearance  it  is 
very  similar  to  that  found  near  Santa  Barbara.  It  lies  in  beds  of 
from  6  inches  to  several  feet  in  thickness,  the  purer  material  being 
on  the  top.  In  some  places  the  deposit  rests  upon  clean  sand,  and 
in  others  upon  sand  that  is  saturated  with  oil. 

The  vein  of  asphalt  is  found  in  a  dike  and  consequently  runs 
parallel  with  the  mountain  range,  is  covered  with  a  soft  brown  rock 
which  can  be  traced  for  several  miles,  indicating  the  existence  of 
asphalt  to  that  extent.  The  vein  is  from  3  to  15  feet  in  width,  and 
is  easily  worked  from  shafts  or  by  drifting. 

The  Southern  Pacific  Eailroad  has  built  a  spur  track  from 
Bakersfield  to  this  deposit,  a  distance  of  about  50  miles.  The 
terminal  has  been  given  the  name  Asphalto. 

The  crude  material  being  analyzed  shows: 

Per  cent. 

Bitumen   78.90 

Mineral  matter 9.40 

Coky  and  volatile  matter -. 4.53 

Water  and  loss 7.17 

100.00 

The  asphalt  is  refined  in  Asphalto  in  much  the  same  manner 
as  that  already  described,  except  that  a  little  heavy  oil  is  added  to 


66  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

assist  in  melting.  Dry  asphalt  and  the  refuse  material  are  used  for 
fuel.  When  it  is  to  be  refined  to  90  per  cent  bitumen,  the  entire- 
operation  of  charging,  boiling,  and  emptying  requires  about 
twenty-four  hours.  The  process  is  continued  till  the  asphalt  be- 
comes hard  enough  to  retain  its  form  at  ordinary  temperatures. 
The  material  is  then  drawn  off  into  boxes  or  barrels  for  shipment. 
It  is  not  ready  for  use  in  pavements  until  it  has  been  fluxed  with 
maltha,  when  it  is  called  paving  cement. 

When,  however,  the  asphalt  is  sold  for  paving  purposes,  this 
fluxing  is  generally  done  at  the  plant,  as  the  maltha,  on  account  of 
its  consistency,  is  not  conveniently  handled.  A  small  quantity, 
however,  is  generally  kept  at  the  plant  where  the  paving  mixture 
is  made,  if  by  chance  the  cement  should  require  some  modifica- 
tion. 

Besides  the  asphalt,  maltha  is  found  in  Asphalto. 

In  Santa  Cruz,  San  Luis  Obispo,  and  Monterey  counties  asphalt 
occurs  of  an  entirely  different  nature.  It  is  called  bituminous  rock, 
and  consists  of  a  natural  mixture  of  bituminous  oil  and  sand.  It 
is  found  in  large  quantities  with  much  variation  in  amount  of  con- 
tained bitumen.  The  sand  is  of  all  grades  of  fineness,  sometimes 
mixed  with  clay  and  so  hard  as  to  be  almost  a  sandstone.  It  makes 
a  good  pavement  in  its  natural  state  when  properly  treated.  The 
early  asphalt  pavements  of  California  were  laid  with  this  material, 
and  when  the  variation  in  amount  of  bitumen,  as  well  as  the  igno- 
rance of  the  industry  .at  that  time,  is  considered,  the  wonder  is  that 
so  many  good  results  were  obtained,  rather  than  that  there  were 
some  failures.  The  material  was  simply  softened  by  heating  on 
the  street  sufficiently  to  allow  it  to  be  smoothly  and  evenly  rolled 
when  it  was  laid  on  the  slightly  prepared  surface.  Doubtless  a  lack 
of  proper  foundation  often  caused  a  failure  in  an  otherwise  fairly 
good  pavement. 

The  larger  portions  of  the  present  California  asphalt  pavements 
were  laid  with  this  material,  and  the  experience  with  these  has  un- 
justly given  a  bad  name  to  California  asphalt  as  a  whole. 

The  first  street  east  of  the  Eocky  Mountains  paved  with  ma- 
terial from  California  was  in  South  Omaha,  Neb.,  in  1891. 


ASPHALT. 


67 


European  Asphalt. 

The  asphalts  from  Europe  from  which  pavements  are  made  are 
found  in  France,  Germany,  Switzerland,  and  in  the  island  of  Sicily. 
(In  a  pamphlet  issued  by  a  Greek  professor  in  1721  he  says  he 
discovered  ten  years  before  a  mine  of  asphalt  in  the  Val  de  Travers 
Canton,  Xeuchatel,  Switzerland,  similar  to  that  existing  in  the 
valley  of  Siddim  near  Babylon.)  Although  somewhat  widely 
separated,  these  asphalts  are  practically  of  the  same  nature,  differ- 
ing somewhat  in  amount  of  bitumen  contained. 

They  are  all  bituminous  limestones.       They  occur  in  strata 


FIG.  1. — POSSIBLE  FORMATION  OF  ROCK  ASPHALT. 

of  varying  depths,  from  6  to  23  feet  in  thickness,  separated  by  im- 
permeable beds  of  stone. 

The  theory  of  the  formation  is  that  at  an  early  geological 
period  bitumen  must  have  been  vaporized  by  extreme  heat,  that 
certain  strata  of  the  limestone  were  softer  than  others,  and  that 
this  bituminous  vapor  was  forced  through  and  along  the  soft 
strata,  as  subterranean  water  follows  any  previous  stratum  con- 
fined by  beds  of  clay  or  rock,  and  that  fissures  in  the  overlying 


68 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


strata  have  allowed  the  vapor  to  pass  to  other  strata  above.  In 
passing,  the  vapor  impregnated  the  particles  of  the  soft  limestone 
to  a  greater  or  less  extent,  and  the  geological  changes  in  the 
subsequent  years  produced  the  rock  asphalt  as  it  exists  to-day. 
Pig.  1  illustrates  this  formation. 

Its  composition  is  almost  entirely  carbonate  of  lime  and  bitu- 
men. To  make  a  good  pavement,  the  rock  should  contain  from  9 
to  11  per  cent  bitumen.  While  this  amount  may  not  be  found  in 
just  the  required  proportions  in  nature,  it  can  be  obtained  by  mix- 
ing a  rock  that  is  rich  in  bitumen  with  one  containing  less,  so  that 
the  compound  shall  contain  the  percentage  desired. 

Published  analyses  of  the  same  mine  differ  considerably,  per- 
haps on  account  of  the  solvents  or  methods  used  by  the  examining 
chemists,  or  possibly  from  an  actual  variation  in  samples  from  the 
same  deposit. 

The  following  are  some  analyses  collected  from  various  authori- 
ties, the  bitumen  and  calcium  carbonate  only  being  considered: 


TABLE  No.  10. 


Ragusa,  Sicily. , 
Seyssel,  France. 


Val  de  Travers,  Switzerland. . 


Vorvohle,  Germany. 
Limner,  " 


Bitumen. 

9.72 

8.92 

8.85 

9.10 

8.15 

7.00 

11.81 

8.00 

10.15 

12.00 

7.00 

12.44 

10.10 

5.35 

14.30 

8.26 


Carbonate 
of  Lime. 

88.75 
88.21 
87.50 
90.35 
91.30 

88.20 
89.55 
88.40 


61.76 
87.95 
90.80 
67.00 
56.54 


Mexican  Asphalt. 

In  the  State  of  Vera  Cruz,  Mexico,  there  are  fifteen  separate 
deposits  of  asphalt;  that  is,  there  are  fifteen  places  where  asphalt 
is  found  at  the  surface. 


ASPHALT. 


Analyses  of  samples  from  the  different  localities  show  the 
material  to  be  identical,  and  it  is  supposed  that  they  are  all  con- 
nected underground,  and  supplied  from  the  same  source. 

These  deposits  as  found  vary  in  width  from  150  to  200  feet,  and 
in  length  from  400  to  600  feet.  The  overflow  from  them  is  very 
great.  In  several  instances  it  forms  a  bed  between  50  and  60  feet 
wide  and  one  or  two  miles  long. 

The  largest  deposit  is  known  as  Lake  Chapapota,  or  in  the  lan- 
guage of  the  natives,  Laguna  Chapapota  ("  Lake  of  Asphalt "). 
This  lake  is  of  irregular  shape  and  of  unknown  depth.  Its  sides  are 
nearly  perpendicular,  as  no  bottom  has  been  found  by  sounding 
three  or  four  feet  from  the  edge. 

Large,  quantities  of  the  material  have  overflowed  in  every  di- 
rection, and  whatever  amount  has  yet  been  taken  from  the  lake,  the 
overflow  still  continues  uninterruptedly.  It  has  been  estimated 
that  1000  tons  per  month  could  be  taken  continually  from  the 
lake  without  in  the  least  lowering  its  surface.  The  amount  in 
sight  has  been  calculated  at  about  300,000  tons. 

Pipes  have  been  sunk  to  a  depth  of  500  feet  near  these  deposits 
which  have  passed  through  vast  beds  of  asphalt.  From  these  pipes 
asphaltic  oil  is  constantly  flowing. 

An  analysis  of  nine  different  samples  of  this  asphalt  in  a  crude 
state  gave  results  as  follows: 

TABLE  No.  11. 


84.04 

82.74 

86.34 

83.70 

87.94 

86.11 

90.14 

87.54 

Wood,  insects,  shells, 
and  leaves  

4  86 

4  76 

2  96 

1  96 

2  36 

3.12 

2.36 

2  56 

Matter  volatile  at  450° 

11.10 

12.50 

10.70 

14.70 

9.70 

10.77 

7.50 

9.90 

The  refined  product  analyzed: 

Per  cent. 

Bitumen   99.47 

Silt  and  lime 53 

100.00 

The  above  analyses  were  made  by  Julius  C.  Schubert  of  New- 
York,  who  recommended  for  a  paving  mixture: 


70  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Per  cent. 

Bitumen    12 

Carbonate  of  lime 15 

Sand   73 

An  examination  of  another  sample  was  made  by  Marriner  & 
Hoskins  of  Chicago.  The  asphalt  was  heated  until  all  the  water 
was  expelled,  and  then  the  temperature  was  gradually  raised  till  the 
thermometer  indicated  400°  F.  and  maintained  there  for  nine 
hours.  The  fluid  was  then  poured  from  the  sediment,,  of  which 
there  was  but  little,  and  analyzed: 

Specific  gravity  at  60°  F 1.069 

Bitumen  soluble  in  ethyl  ether 79.40 

"     petroleum  ether 63.15 

Residue       "          "   turpentine 33.78 

Undissolved  organic  matter 1.72 

Ash 1.25 

Physically, 

at    60°  it  was  tough,  compressible,  and  flexible; 

at    75°  it  was  softer  and  more  flexible; 

at  100°  it  had  the  consistency  of  putty;  beginning  to  flo-w; 

at  300°  there  was  no  flash. 

It  is  claimed  for  this  asphalt  that  it  requires  the  addition  of 
no  flux  whatever  to  prepare  the  asphaltic  cement,  and  that  on  this- 
account,  and  because  of  its  greater  purity,  it  will  resist  successfully 
the  action  of  air  and  water.  Also  it  is  said  that  a  kettle  of  this 
material  was  heated  to  625°  F.  for  ten  hours  without  its  being 
damaged  in  the  least.  This  last  fact  would  avoid  the  liability  to 
injury  on  account  of  overheated  sand,  which  often  occurs  in  using 
the  asphalts  at  present  in  general  use. 

Bermudez  Asphalt. 

In  the  State  of  Bermudez  in  the  northern  part  of  Venezuela 
and  about  one  hundred  miles  from  the  island  of  Trinidad  is  another 
large  deposit  of  asphalt.  It  was  discovered  by  the  early  explorers- 
of  this  region,  but  no  attempt  was  made  to  develop  it  or  put  it  on 
the  market  until  within  the  last  few  years.  It  is  generally  called 
a  lake,  and  is  situated  near  the  San  Juan  Eiver,  about  18  miles 
from  where  it  empties  into  the  Gulf  of  Paria. 


ASPHALT.  71 

The  river  is  navigable  for  vessels  drawing  18  feet  of  water  to- 
this  point,  at  which  is  situated  the  shipping  station  of  the  New- 
York  and  Bermudez  Company,  which  owns  and  controls  the  prop- 
erty. 

The  lake  is  about  5  miles  from  the  point  of  shipment.  It  in- 
cludes an  area  of  some  1200  or  1500  acres  and  is  covered  with 
quite  a  heavy  growth  of  grass  and  bushes.  Its  depth  has  never 
been  determined,  as  in  sounding  it  has  never  been  possible  to  find 
bottom,  and  the  supply  seems  to  be  inexhaustible.  In  hardness  it 
varies  from  the  material  that  is  in  a  soft  fluid  condition  to  the 
hard  brittle  glance  pitch,  but  the  greater  part  is  of  a  medium  grade 
suitable  for  commerce. 

Through  the  lake  runs  a  so-called  stream  of  soft  material,  vary- 
ing in  width  from  100  to  400  feet,  seemingly  in  a  state  of  continued 
motion. 

Over  all  the  surface  except  this  stream  one  can  walk  with  safety 
at  all  times  of  the  day,  but  on  the  stream  itself  it  is  not  safe  to 
venture  after  the  sun  is  a  few  hours  high,  as  the  heat  soon  renders 
it  so  soft  that  a  man  will  sink  into  it  to  quite  a  considerable  dis- 
tance. 

It  is  said  that  a  workman  dug  day  after  day  for  two  years  in 
a  hole  about  G  feet  in  diameter,  and  the  amount  removed  in  the 
daytime  would  be  replaced  at  night,  so  that  the  hole  was  no  larger 
at  the  end  of  two  years  than  at  the  beginning. 

A  narrow-gauge  railroad,  operated  by  steam,  connects  the  lake 
with  the  shipping-point.  The  surface  of  the  asphalt  not  being 
firm  enough  to  sustain  the  weight  of  the  steam-cars,  a  portable 
track  is  laid  out  on  the  lake  upon  which  cars  are  operated  by  hand. 
The  pitch  is  dumped  from  these  hand-cars  into  those  on  the  main* 
line,  which  in  turn  are  drawn  down  to  and  out  upon  the  dock,  when, 
they  are  unloaded  into  vessels  lying  alongside. 

The  first  pavement  laid  with  this  material  was  on  Woodward 
Avenue,  Detroit,  in  1892.  Since  then,  however,  it  has  come  into> 
general  use  in  the  different  cities  of  the  country.  The  crude 
material  is  refined  at  South  Amboy,  N.  J. 

When  refined,  the  asphalt  contains  of  bitumen  97.22  per  cent,, 
mineral  matter  1.50,  and  organic  matter  1.28.  The  bitumen  ia 


72          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

composed  of  petrolene  77.90  and  asphaltene  22.10  per  cent.     The 
specific  gravity  is  1.08. 

*  Kentucky  Asphalt. 

This  material  is  found  in  the  Chester  group  of  subcarboniferous 
rocks  along  the  eastern  and  southern  edge  of  the  western  coal-field 
of  Kentucky.  It  also  exists  in  the  conglomerate  sandstone  of  the 
coal-measure,  but  under  heavy  cover.  Its  principal  localities  are 
in  Breckinridge,  Grayson,  Edmonson,  and  Logan  counties. 

The  deposit  is  really  a  sandstone  impregnated  with  bitumen. 
The  rock  is  not  found  in  distinct  veins,  but  more  in  the  shape  of 
pockets  of  varying  area,  having  a  depth  at  the  centre  often  of  10 
feet.  The  material  is  mined  by  stripping  off  the  overlying  sand- 
stone, leaving  the  bituminous  rock  exposed  and  ready  for  excava- 
tion. The  stone  is  fine-grained  and  nearly  all  silica,  carrying  on 
an  average  some  8  per  cent  of  bitumen,  but  at  times  as  much  as 
12  per  cent. 

After  the  bitumen  is  extracted,  the  rock  analyzes: 

Per  cent. 

Silica 96.88 

Sesquioxide  of  iron 0.81 

Alumina    0.46 

Lime 0.34 

Magnesia    0.20 

Soda    0.81 

Potash 0.20 

Combined  water  and  loss 0.25 


99.95 

In  preparing  the  rock  for  paving  purposes  it  is  first  ground  in 
mills  consisting  of  horizontal  plates  to  which  raised  lugs  are  at- 
tached revolving  at  a  high  rate  of  speed.  The  rock  is  broken  by 
impact  and  carried  by  centrifugal  force  through  a  screen  surround- 
ing the  mill.  After  leaving  the  mill  and  passing  a  second  screen, 
the  powder  is  borne  by  elevators  to  revolving  heaters,  where,  after 
being  raised  to  a  proper  temperature,  it  is  taken  to  the  street  and 
laid  in  the  usual  manner.  The  entire  operation  of  grinding  and 
heating  is  automatic,  the  rock  not  being  touched  by  hand  from 

*  From  a  paper  by  Marshall  Morris.     Read  before  the  St.  Louis  Engineers' 
Club. 


ASPHALT.  73 

«• 

the  time  it  is  placed  in  the  elevators  to  be  carried  to  the  mills  till 
it  is  delivered  on  the  street.  Care,  however,  is  required  in  selecting 
the  rock  for  the  crushing  so  that  the  product  may  contain  the 
required  amount  of  bitumen  when  placed  in  the  pavement. 

Portions  of  two  streets  in  Brooklyn,  X.  Y.,  were  paved  success- 
fully with  this  material  in  1889. 

In  1890  a  small  amount  was  laid  on  a  sidewalk  at  the  wagon- 
entrance  of  the  Adams  Express  Co.  in  Louisville,  Ky.  Since  that 
time  it  has  been  used  with  good  results  in  many  other  cities,  but 
most  extensively  in  Buffalo,  N.  Y.,  in  conjunction  with  the  German 
rock  asphalts,  and  also  in  St.  Louie,  Mo.  It  has,  however,  been 
successfully  used  in  combination  with  the  limestone  asphalts  of 
Texas  and  Indian  Territory. 

The  proportion  generally  recommended  in  connection  with  the 
foreign  asphalts  is: 

Per  cent. 

Kentucky  rock 70  to  80 

Gterman         "    30  to  20 

Texas  Asphalt. 

The  asphalt  deposits  of  Texas  are  in  Uvalde  County.  There 
are  two  areas  of  bituminous  rock,  one  in  the  extreme  western  por- 
tion of  the  county  along  the  courses  of  the  Turkey,  Gato,  and 
Olmos  creeks,  and  the  other  near  the  Nueces  River  near  the  South- 
ern Pacific  Railroad.  The  first-mentioned  lies  along  these  creeks 
in  a  continuous  area  about  4£  miles  long  north  and  south,  and  half 
a  mile  or  more  in  width.  The  asphalt  occurs  as  an  impregnation 
of  a  porous  limestone. 

The  principal  mining  is  done  at  Carbonville,  about  6  miles  from 
the  Cline  station  of  the  Southern  Pacific  Railroad.  The  quarries 
are  easily  worked,  as  there  is  very  little  overlying  material  to  be 
removed.  The  rock  is  treated  on  the  spot  and  is  sold  in  two  con- 
ditions, as  a  mastic  and  as  a  gum. 

The  mastic  is  prepared  by  grinding  the  rock  to  the  required 
fineness,  when  it  is  melted  and  run  into  moulds,  and  when  cool  is 
ready  for  shipment.  This  product  is  used  for  pavements  and  is 
further  treated  by  the  addition  of  sand,  residuum  oil,  etc.,  as  may 


74  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

be  required  at  the  place  where  it  is  to  be  laid.  A  portion  of  a 
street  in  Houston,  Texas,  has  been  paved  with  this  material,  and 
it  has  also  been  used  to  some  extent  in  New  York  City. 

The  gum,  however,  is  more  valuable  commercially.  This  is 
prepared  by  dissolving  out  the  bitumen  from  the  rock  with,  benzine. 
The  benzine  is  then  distilled  off  and  used  over  and  over  again  with 
but  little  loss.  The  bitumen  is  obtained  in  an  almost  pure  state. 

Two  different  samples  of  the  rock  analyzed  as  follows: 

Per  cent. 

No.  1  bitumen 25.18 

Organic  matter 1.46 

Mineral  residue 73.36 

100.00 

No.  2  bitumen  extracted  by  petroleum  naphtha  (petrolene) .  .      6.40 
"    chloroform  (asphaltene) 2.63 

Total  bitumen 9.03 

Mineral,  residue .   90.97 


100.00 

The  mineral  residue  was  found  to  be  carbonate  of  lime  with 
an  appreciable  amount  of  oxide  of  iron  and  a  trace  of  magnesia. 
Although  the  above  samples  show  quite  a  difference  in  the  amount 
of  bitumen,  the  average  is  from  14  to  15  per  cent. 

Nueces  Biver  Deposits. 

The  bituminous  rock  in  this  locality  is  a  sandstone.  Its  area 
extends  from  a  point  on  the  Nueces  Eiver  about  9  miles  below  the 
Southern  Pacific  Eailroad  for  more  than  3  miles.  Its  width  has 
not  been  determined.  It  outcrops  in  places  along  the  river,  and 
at  Waxy  Falls  a  stratum  of  sandstone  bearing  some  bitumen  was 
found  10  feet  thick  about  25  feet  below  the  top  of  the  bluff.  Next 
T)elow  this  is  another  stratum,  5  feet  in  thickness,  containing  so 
much  bitumen  that  under  the  heat  of  the  sun  it  oozes  out  over  the 
surface. 

Samples  of  rock  taken  from  the  outcrop  near  Waxy  Falls  upon 
analysis  gave  the  following  results: 


ASPHALT.  75 

Per  cent. 

At  the  surface,  bitumen 13.24 

Two  feet  below  the  surface,  bitumen 15.03 

Sand 74.03 

Oxides  of  iron  and  alumina 7.76 

Organic  matter,  water  and  undetermined 3.18 

100.00 
Four  feet  below  the  surface,  bitumen 12.36 

Utah  Asphalt  (Gilsonite). 

Quite  a  deposit  of  bitumen  of  a  very  pure  quality  exists  in  the 
eastern  part  of  Utah  and  the  western  portion  of  Colorado.  It  is 
called  "  Gilsonite  "  from  Mr.  S.  H.  Gilson  of  Salt  Lake  City.  It 
is  mined  in  the  counties  of  Uintah  and  Wasatch,  Utah  and  Clear 
Creek  Co.,  Colorado. 

Physically  it  is  a  black  substance,  quite  hard  and  very  brittle, 
"breaking  with  a  conchoidal  fracture.  It  has  a  brilliant  lustre  and 
in  appearance  is  much  like  glance  pitch.  It  occurs  in  veins  of 
from  one-sixteenth  of  an  inch  to  18  feet  in  thickness,  and  some- 
times extending  a  distance  of  10  miles. 

These  veins  were  originally  cracks  in  the  rock  which  in  some 
iray  have  become  filled  with  the  gilsonite  presumably  at  the  same 
time  the  rupture  occurred,  as  pieces  of  rock  are  frequently  found 
entirely  separated  from  the  adjacent  walls.  The  theory  is  that  the 
gilsonite  while  in  a  plastic  state  was  forced  into  the  rock-fissure 
"by  some  unknown  force.  No  attempt  has  been  made  to  explain  the 
previous  condition  of  the  material. 

There  are  six  well-defined  veins  of  this  material,  and  the  follow- 
ing estimate  has  been  made  of  their  contents: 

Tons. 

Duchesne  vein 941,916 

Culmer  vein .' 410,666 

East  and  West  Bonanzas 10,504,000 

Cowboy  vein 8,888,000 

Black  Dragon  vein 3,000,000 


23,744,582 


It  is  easily  mined,  as  it  yields  readily  to  the  common  pick  and 
"breaks  freely  upon  the  rock,  and  requiring  no  sorting  after  a  depth 
is  reached  below  the  influence  of  the  atmosphere. 


76          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

The  above  veins  are  from  100  to  200  miles  from  a  railroad,  and, 
on  account  of  the  roughness  of  the  country,  the  transportation 
charges  are  heavy. 

Gilsonite  is  used  chiefly  in  the  arts  and  manufactures,  but  it  is 
sometimes  added  to  other  bitumens  for  paving  mixtures. 

It  is  wholly  soluble  in  carbon  bisulphide,  and  partially  so  in 
ordinary  ether,  alcohol,  petroleum  ether,  and  chloroform.  Chemi- 
cally it  is  composed  of: 

Per  cent. 

Carbon 88.30 

Hydrogen  9.96 

Sulphur 1.32 

Ash 0.10 

Oxygen  and  nitrogen 0.32 


100.00 

Since  the  above  analysis  was  made,  Prof.  Day  says  that  a  further 
investigation  shows  the  nitrogen  to  be  1.96  per  cent,  and  he  thinks 
the  figures  for  hydrogen  are  correspondingly  too  high. 

Bituminous  limestone  has  also  been  found  in  Utah,  but  it  has 
never  been  mined  to  any  great  extent. 

Indian  Territory  Asphalt. 

The  asphalt  deposits  of  this  section  are  located  in  the  south- 
western part  of  the  Territory,  in  the  Arbuckle  Mountains  near  the 
Washita  Eiver.  They  extend  over  an  area  of  several  square  miles. 
The  asphalt  is  found  in  composition  with  sand  and  also  as  bitumi- 
nous rock.  The  former  contains  16J  per  cent  and  the  latter  21  per 
cent  of  bitumen.  The  same  asphalt  is  used  in  pavements  in  its 
natural  state.  It  is  heated  in  a  special  apparatus  and  laid  in  much 
the  same  way  as  the  European  rock  asphalts.  To  the  rock  asphalt, 
however,  50  per  cent  of  sand  asphalt  is  added  before  heating,  when 
it  is  laid  as  before.  Nearly  all  the  work  in  the  development  of 
this  deposit  has  been  done  in  the  last  few  years,  the  charter  of  the 
company  from  which  the  present  company  leases  it  having  been 
granted  in  1895. 

Where  the  material  has  been  used  it  has  given  good  satisfaction, 
though  a  soft  pavement  would  naturally  be  expected  from  one  con- 
taining so  great  an  amount  of  bitumen. 


ASPHALT.  77 

By  a  process  of  refining,  a  bitumen  of  about  the  consistency  of 
maltha  is  produced  when  required.  It  is  first  separated  from  the 
sand  by  being  boiled  in  water.  The  bitumen,  having  a  less  specific 
gravity  than  the  water,  rises  to  the  surface,  when  it  is  skimmed  off, 
and  the  operation  continued  as  long  as  desired. 

Montana  Asphalt. 

A  deposit  of  bitumen  generally  termed  asphalt,  but  not  strictly 
BO  under  the  definition  previously  given  in  this  chapter,  is  found 
in  Montana.  At  ordinary  temperatures  it  is  soft  and  will  pour 
slowly.  Upon  being  treated  with  carbon  bisulphide,  95  per  cent 
was  dissolved.  Treated  with  gasolene  80  per  cent  was  found  to 
be  petrolene,  the  insoluble  matter  in  both  cases  being  leaves,  feath- 
ers, bugs,  flies  and  other  insects.  The  deposit  has  never  been  de- 
veloped commercially. 

Cuban  Asphalt. 

There  are  four  distinct  submarine  deposits  of  asphalt  situated 
in  the  Bay  of  Cardenas,  all  within  twenty  miles  of  the  city  of  the 
same  name. 

The  first  is  in  the  western  part  of  the  bay  and  is  practically 
pure  bitumen.  It  is  used  principally  in  the  manufacture  of 
varnishes.  It  has  been  mined  here  since  about  1870  by  sinking 
a  shaft  some  125  feet  deep  in  the  bottom  of  the  bay.  The  opera- 
tion of  mining  is  very  simple.  A  lighter  is  moved  over  the  shaft 
and  a  long  iron  bar,  pointed  at  the  end,  is  dropped  so  that  its  own 
weight  detaches  portions  of  the  asphalt  with  which  it  comes  in 
contact.  The  operation  is  repeated  until  a  sufficient  quantity  has 
been  detached,  when  a  diver  loads  it  into  nets  and  it  is  hoisted  to 
the  surface. 

The  other  deposits  produce  a  lower  grade  of  material  which  is 
suitable  for  pavements.  They  are  operated  in  practically  the  same 
manner  as  that  just  described.  The  largest  of  these  is  about  15 
miles  from  the  cit}r,  near  Diana  Cay.  It  has  been  operated  since 
1870,  producing  some  1000  tons  per  year  without  any  apparent 
diminution  in  the  supply.  This  deposit  seems  to  be  inclosed 
within  a  circumference  of  about  150  feet  and  in  water  12  feet 
deep. 


78  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

There  are  also  deposits  of  asphalt  near  Puerto  Padre  on  the 
north  coast  of  the  island,  as  well  as  some  liquid  bitumen  near 
Santiago  de  Cuba. 

Barbadoes  Asphalt. 

A  variety  of  bitumen  known  as  "  glance  pitch  "  has  been  known 
for  some  time  on  the  island  of  Barbadoes.  It  is  a  hard  brittle 
asphalt,  breaking  with  a  clear  brilliant  fracture.  It  occurs  in  veins 
from  an  inch  to  a  foot  in  thickness.  It  has  never  been  used  in, 
and  is  not  suitable  for,  pavements,  but  its  output  is  entirely  con- 
sumed in  the  manufacture  of  varnishes,  etc.  It  is  almost  wholly 
soluble  in  carbon  bisulphide. 

Asphalt  in  Turkey. 

An  important  asphalt  mine  is  located  near  Avalona  on  the 
Adriatic  Sea.  It  belongs  to  the  Sultan,  but  has  been  leased  to  a 
French  syndicate.  The  material  is  taken  out  in  both  a  solid  and 
a  liquid  state  and  is  exported  to  Europe  and  America.  There  are 
also  other  mines  in  the  interior  of  Turkey  in  Asia  belonging  to 
the  government  and  private  parties,  but  they  have  not  been  worked 
to  any  extent  on  account  of  the  bad  transportation  facilities. 

Dead  Sea  Asphalt. 

About  the  Dead  Sea  there  is  quite  a  quantity  of  asphalt  be- 
longing to  the  government.  It  is  not  used  for  any  purpose,  and 
persons  found  collecting  it  are  fined  or  otherwise  punished.  It  is 
said  that  in  former  times  asphalt  was  frequently  found  floating  on 
the  surface  of  the  Dead  Sea,  especially  after  earthquakes. 

Syrian  Asphalt. 

There  are  four  asphalt  mines  in  Syria,  but  the  one  at  Hasbaya 
is  the  most  important.  The  mine  'has  been  worked  at  intervals  by 
different  lessees  since  1864,  but  only  1000  tons  per  annum  were 
taken  out  when  actual  operations  were  carried  on.  It  is  the 
private  property  of  the  Sultan,  and  has  not  been  worked  to  any 
extent  since  1893.  From  1882  to  1892  about  $70,000  worth  of  this 
material  was  exported  to  the  United  States,  and  in  1897  $3439 
worth.  In  1893  the  product  was  worth  about  $90  per  ton. 


1  ASPHALT.  79 

It  is  said  that  asphalt  exists  in  this  vicinity  in  large  quantities, 
and  under  a  favorable  government  thousands  of  tons  might  be 
mined  each  year. 

A  sample  of  the  Hasbaya  product  is  thus  described:  It  is 
black  with  a  bright  jetlike  lustre, making  a  blackish-brown  streak  on 
unsized  paper.  It  is  so  brittle  that  pieces  may  easily  be  broken  off 
with  the  fingers.  It  is  very  combustible,  but  a  splinter  held  in  the 
flames  will  melt  before  igniting.  Its  specific  gravity  is  1.104. 

Egyptian  Asphalt. 

No  natural  asphalt  is  found  in  Egypt  except  in  very  small  quan- 
tities above  Suakim  near  Abyssinia,  where  it  cannot  be  worked 
profitably,  and  some  small  deposits  on  the  east  coast  of  the  Bed 
Sea. 

It  is  said,  however,  that  two  firms  in  Egypt  manufacture  arti- 
ficial asphalt,  importing  material  for  their  use  from  Italy,  France, 
and  England.  What  their  process  was,  or  to  what  uses  their  prod- 
uct was  put,  could  not  be  learned. 


CHAPTER  IV. 

BRICK-CLAYS   AND  THE   MANUFACTURE   OF   PAVING-BRICK. 

THE  word  clay  as  ordinarily  used  means  any  earthy  substance 
which  can  be  worked  up  with  water  into  a  plastic  mass  that  when 
dried  will  retain  any  shape  into  which  it  may  have  been  formed. 
Strictly  speaking,  the  term  applies  to  a  single  mineral,  hydrated 
silicate  of  alumina,  or  kaolin.  It  is  not,  however,  a  natural  mineral, 
but  is  the  product  of  the  decomposition  of  feldspar. 

Beds  of  feldspar  have  often  been  found  covered  by  the  kaolin 
formed  by  the  decomposition  of  a  portion  of  its  mass.  This  occurs 
when  the  feldspar  is  exposed  to  the  action  of  water  containing 
carbonic  acid  gas,  which  acts  upon  the  alkaline  base  of  the  mineral 
and  carries  it  away  in  solution,  leaving  the  silicate  of  alumina  be- 
hind. As,  however,  feldspar  is  seldom  found  in  large  quantities  by 
itself,  so  deposits  of  pure  kaolin  are  very  rarely  found.  Com- 
mercially  they  are  of  considerable  value. 

When  pure,  kaolin  is  composed  of: 

Per  cent. 

Silica 46.3 

Alumina 39.8 

Water 13.9 

This  is  represented  chemically  by  the  formula  Al2032Si022H2(X 
It  is  the  base  of  all  the  substances  known  as  clays,  and  as  they  are 
formed  by  the  decomposition  of  rocks,  so  their  chemical  composi- 
tion varies  with  that  of  the  rocks  from  which  they  are  derived. 

Quartz  and  feldspar  are  the  two  minerals  found  in  the  greatest 
abundance  in  the  earth's  crust,  and,  very  naturally,  it  is  expected 
to  find  sand  and  clay  as  the  most  common  of  the  products  of  the 
decomposition  of  rocks. 

80 


BRICK-CLAYS—  MAN  UFA  CTURE  OF  PAVING-BRICK.        81 

Feldspars  are  divided  into  three  separate  varieties:  orthoclase, 
or  potash  feldspar;  albite,  or  soda  feldspar;  and  anorthite,  or  lime 
feldspar, — each  of  these  varieties  being  minerals  more  or  less  com- 
plex. These,  too,  are  at  all  times  in  the  same  mineral,  which  must  be 
named  by  one  of  the  terms  used  in  the  classification,  the  one  in 
greatest  abundance  giving  the  character  to  the  compound. 

All  feldspars  are  acted  upon  by  the  atmosphere.  The  oxygen, 
carbonic  acid,  and  water  contained  in  it,  when  taken  together,  form 
a  solvent  that  is  hard  for  rocks  to  resist,  especially  when  supple- 
mented by  soil-waters  containing  more  or  less  acids  derived  from 
decaying  vegetable  products. 

Under  these  influences  granites  and  other  rocks  containing 
feldspar,  especially  the  potash  variety,  are  rapidly  decomposed. 
The  feldspar  having  lost  its  cementing  property,  the  rock  falls  into 
pieces.  The  carbonate  of  potash  is  dissolved  in  the  water  and 
borne  away.  The  particles  of  quartz,  mica,  and  other  accessory 
minerals  remain  and  become  assimilated  with  silicate  of  alumina 
from  the  feldspar,  all  together  making  up  the  product  commonly 
called  clay.  It  can  be  readily  seen  that  it  cannot  be  a  pure  mineral 
and  that  its  composition  must  vary  greatly. 

Kaolin  has  a  specific  gravity  of  from  1.5  to  2.2  and  is  white  in 
color.  It  is  soft  to  the  touch  when  dry,  and  very  plastic  when 
wet.  It  has  two  marked  chemical  characteristics,  insolubility  and 
infusibility.  It  being  the  product  of  a  soluble  body,  the  former 
might  be  expected.  It  is  not  affected  by  ordinary  chemical  agents, 
nor  by  temperatures  that  have  thus  far  been  produced  in  the  arts. 
It  is  consequently  of  greatest  value  in  the  manufacture  of  crucibles 
and  other  refractory  utensils  used  in  chemical  research. 

While  this  infusibility  is  true  of  kaolin,  it  is  not  true  of  clay. 
For  the  addition  of  different  minerals  found  in  nature  often  forms 
a  compound  that  is  easily  fused.  These  minerals  when  thus  used 
are  called  fluxes.  Naming  them  in  the  order  of  their  effectiveness, 
they  are  potash,  soda,  iron,  lime,  and  magnesia.  Very  small 
amounts  of  one  or  more  of  these  substances  are  required  in  any  clay 
to  destroy  its  value  as  a  refractory  material. 

But  on  the  other  hand  the  finely  divided  silica  of  the  original 
rock  which  is  always  found  in  a  greater  or  less  amount  in  most 
kaolin  detracts  not  at  all  from  its  heat-resisting  qualities,  the  silica 


82  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

itself  being  practically  infusible.  For  this  reason  free  silica  is  prac- 
tically the  only  impurity  that  is  permissible  in  kaolin  without  de- 
tracting from  its  refractory  material. 

Feldspar  and  mica  are  found  in  nearly  all  clays,  the  latter  often 
being  discernible  to  the  naked  eye.  The  former,  however,  cannot 
be  thus  distinguished  from  free  silica.  These  two  minerals  both 
contain  alkalies  in  combination  with  silica  and  alumina,  and  so  it 
is  understood  how  alkalies  can  be  discovered  in  clays  by  analysis, 
when  it  would  not  be  expected  to  find  them  existing  in  a  free  state 
in  a  mineral  whose  origin  was  due  to  the  action  of  water  and  other 
solvents. 

The  oxides  and  other  compounds  of  iron  are  generally  found  in 
clays.  The  sesquioxide  and  the  protoxide  are  the  most  common 
forms,  but  carbonates  are  not  uncommon,  and  sulphides  are  oc- 
casional as  well  as  injurious  impurities.  Iron  gives  the  color  to 
clays.  The  tints  vary  from  buff  to  red,  and  from  drab  to  blue  or 
green,  the  amount  of  iron  not  seeming  to  determine  the  degree  of 
color.  The  effect,  too,  of  iron  is  very  much  heightened  and  changed 
by  heat.  The  colors  produced  by  burning  vary  from  cream  to  per- 
fectly black,  with  nearly  all  the  intervening  tints  and  shades, 
though  the  reds,  browns,  and  greens  are  most  common.  A  hand- 
some cream-colored  brick  is  made  at  Milwaukee,  and  others  of  pink 
color  in  certain  parts  of  Canada. 

Organic  matter  is  frequently  found  in  clays,  but  it  is  of  little 
importance.  It  is  generally  caused  by  the  presence  of  decomposing 
carbonaceous  matter.  It  gives  a  color  to  the  clay,  but  when  sub- 
jected to  even  a  comparatively  low  heat  it  is  easily  driven  off.  It  is 
very  seldom,  therefore,  that  its  presence  is  detrimental. 

Clay  can  then  be  called  a  compound  of  a  clay  base  with  sand, 
feldspar,  mica,  and  other  silicates  colored  by  iron  oxides  or  organic 
matter. 

The  properties  of  clays  by  which  their  values  are  determined 
are:  plasticity,  so  that  when  wet  it  is  possible  to  shape  it  into  any 
desirable  form;  >  the  maintenance  of  this  form,  while  it  is  being 
burnt,  to  such  a  degree  that  its  shape  is  permanent;  and  its  re- 
fractoriness, so  that  it  is  able  to  withstand  great  and  long-con- 
tinued heats  without  fusing. 

Plasticity  is  a  property  that  is  shared  by  practically  all  Delays. 


BEICK-CLA YS— MANUFACTURE  OF  PAVING-BRICK.        83 

As  a  rule  they  all  tend  towards  crystallization,  and  some  kaolins  are 
made  up  of  masses  of  unattached  scales.  These  are  slightly  plastic 
and  can  be  made  more  so  by  grinding  and  kneading  in  water,  when 
an  examination  shows  that  the  crystalline  structure  has  been  broken 
up.  Naturally,  plastic  clays  do  not  show  this  structure,  indicating 
that  a  clay's  plasticity  depends  upon  the  extent  to  which  this 
structure  has  been  destroyed. 

In  several  places  clays  are  found  that  are  entirely  free  from 
plasticity,  even  after  being  ground  and  treated  with  water.  Frost 
and  the  action  of  water  disintegrate  them  and  a  fine  sand  is  formed, 
but  a  chemical  analysis  shows  them  to  be  almost  pure  kaolin. 

Permanence  of  form  in  clay  ware  is  caused  by  heat.  In  ancient 
times  and  in  dry  climates  bricks  that  were  only  dried  in  the  sun  have 
lasted  for  a  considerable  time,  but  they  could  not  be  called  per- 
manently shaped. 

Generally  speaking,  if  heat  has  been  applied  only  sufficiently 
to  drive  out  the  water  mechanically  mixed,  the  mass  will  be  porous, 
somewhat  shrunken  in  form,  and  readily  disintegrated  under  the 
action  of  the  elements.  If,  however,  the  heat  be  increased  and 
continued,  the  clay  will  shrink  farther  and  harden,  until,  when  the 
proper  point  is  reached,  a  new  material  has  been  formed  which 
is  practically  indestructible.  If  the  heat  be  continued  still  further, 
the  clay  will  become  harder,  more  brittle,  and  often  deformed. 
Other  clays  will  melt  and  become  glassy  and  lavalike,  as  is  so  often 
seen  in  arch-bricks  of  an  old-fashioned  wood-burning  kiln. 

Argillaceous  matter  as  a  whole  is  divided  into  two  classes,  clays 
and  shales.  Chemically  they  are  often  the  same.  Physically  the 
shales  can  be  detected  by  their  stratified  or  laminated  structure. 
They  are  hard  and  compact,  and  require  considerable  work  to  pre- 
pare them  for  use.  Like  the  different  kinds  of  granite,  clays  merge 
into  shales  and  shales  into  clays,  so  that  the  line  separating  them 
must  be  an  arbitrary  one. 

Shales  must  not  be  confounded  with  slates,  which  they  very 
much  resemble.  Slates  have  been  formed  by  the  action  o,f  heat 
combined  with  great  pressure.  They  are  hard  and  durable  rocks, 
•while  shales  will  rapidly  disintegrate  when  exposed  to  the  action  of 
the  atmosphere. 

As  a  rule  shales  'are  formed  in  deeper  water  than  clays.    Their 


34          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

laminations  are  supposed  to  have  been  caused  by  the  intermittent 
deposit  of  the  material  of  which  they  are  formed,  by  pressure,  or 
by  both. 

According  to  their-  composition,  clays  are  divided  into  high- 
and  low-grade  clays.  The  first  comprises  clays  and  shales  that  con- 
tain in  conjunction  with  not  less  than  50  per  cent  of  kaolin  base 
little  else  than  finely  divided  silica.  The  other  constituents  rarely 
exceed  5  per  cent  and  are  often  as  low  as  3  per  cent.  The  second 
division  includes  all  other  clays  and  shales.  They  may  run  from 
10  to  70  per  cent  of  kaolin  base,  but  always  contain  a  large  amount 
of  fluxing  material.  The  alkalies  compose  from  2  to  5  per  cent, 
while  lime,  magnesia,  and  iron  add  two  or  three  times  as  much 
more.  As  a  rule  the  clays  of  the  first  division  are  refractory,  and 
those  of  the  second  fusible. 

Clays,  however,  are  popularly  classified  into  fire-clays,  shales, 
and  mud-clays.  The  first  is  a  refractory  clay  of  a  high  grade  that 
cannot  be  fused  at  any  temperature  used  in  the  arts.  It  is  also 
subdivided  into  non-plastic  and  plastic  varieties.  The  former  are 
something  of  the  nature  of  rocks,  but  upon  exposure  to  the  weather 
they  crumble  into  fine  particles  similar  to  sand.  With  ordinary 
grinding  they  show  no  plasticity  whatever,  and  would  thus  seem 
to  want  one  of  the  main  clay  characteristics,  but  an  analysis  plainly 
shows  their  true  character,  while  continued  and  repeated  grinding 
develops  plasticity. 

Plastic  fire-clays  differ  from  mud-clays  in  the  chemical  com- 
position, which  gives  them  their  refractory  qualities.  Kaolin  or 
pure  clay  is,  as  has  already  been  said,  practically  infusible,  but  it  is 
seldom  found  in  a  pure  state.  The  great  mass  of  clays  distributed 
over  the  earth's  surface  is  impure,  and  upon  the  quantity  and  qual- 
ity of  the  impurities  depends  the  fusibility  and  refractoriness  of 
the  clay. 

The  principal  impurity  is  quartz,  which  is  not  fusible  at  or- 
dinary temperatures  used  in  manufacturing,  so  that  the  fluxing  ele- 
ments of  a  clay  are  generally  considered  to  be  its  impurities  except 
quartz.  Lime  and  magnesia  are  valuable  as  fluxes,  except  when 
they  are  present  as  carbonates  in  any  considerable  quantity,  as  they 
then  lower  the  melting-point  of  the  clay  and  a  hard,  tough  brick 
cannot  be  produced  by  the  burning.  The  condition  of  iron  is  also 


BRICK-CL ATS— MANUFACTURE  OF  PAVING-BRICK.        85 

important,  free  oxide  being  the  least  injurious.  The  more  evenly 
it  is  scattered  through  the  clay  the  better,  so  that  vitrification  may 
be  as  regular  and  even  as  possible. 

Just  how  much  of  these  fluxes  can  exist  in  a  clay  without  de- 
stroying its  refractory  properties  is  uncertain.  It  depends  greatly 
upon  the  character  of  the  clay  as  well  as  upon  the  nature  and 
number  of  the  fluxes.  Generally  the  finer-grained  and  less  dense 
a  clay  is  the  more  easily  it  is  fused.  The  limit  of  the  fluxes  is 
probably  from  5  to  7  per  cent. 

In  the  Eeport  of  the  Geological  Survey  of  Ohio  analyses  of 
fourteen  different  fire-clays  used  in  the  manufacture  of  paving- 
brick  and  sewer-pipe  are  given.  The  average  of  these  showed 
93.41  per  cent  of  clay  and  sandy  matter,  with  5.65  per  cent  of  iron 
and  fluxes. 

In  commenting  on  this,  it  is  said  that  this  would  indicate  a 
clay  more  fusible  than  the  stone-  and  yellow-ware  clays,  but  far 
less  fusible  than  the  shales;  also  that  the  facts  prove  this,  as  the 
above  clays,  while  vitrifying  very  well  up  to  a  thickness  of  two 
inches,  are  very  difficult  to  vitrify  when  made  into  a  brick  or  block. 

The  same  authority  gives  the  analyses  of  ten  shales  used  for 
paving-brick  and  sewer-pipe.  The  average  composition  of  these 
was: 

Per  cent. 

Clay  and  sand 84.78 

Fluxes  13.22 

98.00 

Enough  has  already  been  said  to  show  the  difference  between 
fire-clays  and  shales.  Their  product  also,  when  burned,  is  very 
different.  The  shales,  containing  so  much  more  of  the  fluxing  ele- 
ments, can  be  more  completely  vitrified.  A  shale  brick  is  harder, 
denser,  and  more  brittle  than  one  made  of  fire-clay.  The  latter 
absorbs  more  water,  but  is  tougher.  The  advocates  of  both  kinds 
claim  all  the  virtues  for  their  own  product  and  allow  very  little  to 
their  rivals.  It  is  certain,  however,  that  good  pavements  have  been 
laid  with  both  varieties,  and  good  results  will  be  obtained  if  proper 
judgment  be  used  in  the  selection,  whichever  kind  is  used. 

In  "  Mineral  Resources  for  1897  "  the  following  tables  are  given 


86 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


showing  three  stages  of  transformation  of  a  German  porphyry  into 
kaolin,  Table  No.  12  giving  the  mechanical  analysis  and  No.  13  the 
chemical  composition  of  the  rock  at  its  corresponding  change. 
No.  1  is  the  original  porphyry,  No.  2  an  intermediate  stage,  and 
No.  3  the  resulting  kaolin. 


TABLE  No.  12. 

No.  1. 

Coarse  sand 33.95 

Fine  sand 36.20 

Finest  sand 7.90 

Clay 9.27 

Fine  clay 7.46 

Finest  floating  particles 5.22 


100.00 


TABLE  No.  13. 


SiO2    .  . 

No.  1. 
77  48 

A12O3   

17.10 

Jte2O8    

2.83 

MnO 

84 

CaO   

38 

MgO    . 

10 

K.,0 

1  03 

NaoO                 

13 

P,O    . 

.    Trace 

No.  2. 

22.56 

37.40 

12.15 

12.26 

8.55 

7.08 

100.00 


No.  2. 

75.73 

21.92 

.98 

.18 

.27 

.10 

.55 

.08 


No.  3. 

2.48 
28.52 
18.42 
20.51 
17.69 
12.38 

100.00 


No.  3. 

76.48 

21.58 

.97 

.17 

.25 

.07 

.16 

.01 


99.89 


99.81 


99.69 


The  word  "  vitrification  "  is  defined  in  the  Century  Dictionary 
as  "  conversion  into  glass,  or  in  general  into  a  material  having  a 
glassy  or  vitreous  structure  ";  and  "  vitreous  "  as  "  resembling  glass, 
glassy  ";  but  these  same  words  as  applied  to  brick  or  sewer-pipe 
have  come  to  receive  a  very  different  meaning.  A  glassy  brick 
would  not  make  a  good  pavement.  It  would  be  smooth  and  brittle. 

As  applied  to  brick  the  term  vitrified  means  that  a  chemical 
action  has  taken  place  so  that  the  clay  particles  have  coalesced  and 
become  fused  by  the  action  of  heat,  forming  a  solid  new  homogene- 
ous whole,  but  not  that  the  fusion  has  been  made  complete  and  the 
entire  mass  brought  to  a  semi-liquid  condition.  In  some  clays  the 


BRICK-CLAYS— MANUFACTURE  OF  PAVING- BRICK.        87 

character  of  the  material  is  such  that  the  proper  chemical  uoion 
for  vitrification  will  not  take  place,  so  that  the  brick  absorbs  water 
no  matter  to  what  heat  it  may  have  been  subjected,  and  accordingly 
will  not  vitrify  in  this  sense  of  the  word.  Many  engineers,  there- 
fore, have  decided  upon  the  absorption  test  as  the  proper  one  to 
determine  to  what  degree  a  brick  has  become  vitrified.  A  thor- 
oughly vitrified  brick  breaks  with  a  smooth  conchoidal  fracture  and 
has  no  visible  pores.  The  burned  particles  and  granulated  structure 
so  plainly  discerned  in  a  half-burned  building-brick  have  all  dis- 
appeared. 

A  clay  from  which  such  brick  can  be  successfully  and  profitably 
made  must  be  both  fusible  and  refractory.  Unless  it  be  fusible 
the  product  will  not  vitrify  at  all,  and  yet  if  it  have  this  property 
in  too  great  a  degree,  the  clay  will  melt  and  lose  its  shape  upon  the 
application  of  great  heat.  It  should  be  sufficiently  refractory  to 
allow  the  vitrifying  heat  to  be  applied  within  considerable  limits, 
so  that  if  the  temperature  be  increased  a  hundred  degrees  or  more 
after  vitrification  has  set  in,  the  form  of  the  brick  will  not  be  in- 
jured. The  more  equally  refractoriness  and  fusibility  can  be  op- 
posed to  each  other,  with  neither  property  being  pushed  to  extremes 
by  the  heat  used  by  the  average  burner,  the  greater  will  be  the 
percentage  of  the  finished  product  of  the  kiln. 

The  proper  amount  of  plasticity  must  also  be  obtained.  If  it 
be  too  small,  the  clay  particles  will  not  assimilate  in  the  new  state, 
so  that  when  burned  the  material  will  be  porous  and  have  little  co- 
hesive strength.  If,  on  the  other  hand,  it  be  too  plastic,  the 
mud  will  retain  its  shape  and  position  to  such  an  extent  after  being 
machined  that  the  twist  given  the  clay,  especially  if  an  auger 
machine  be  used,  is  often  plainly  visible  in  the  finished  product 
and  laminations  are  formed  with  appreciable  voids  between  the  dif- 
ferent layers,  thus  reducing  the  strength  of  the  brick.  These,  how- 
ever, are  mechanical  faults  and  can  be  easily  corrected  by  a  study 
of  the  crude  material  and  the  application  of  the  proper  remedy. 
Shales  as  a  rule  are  less  plastic  than  clays  and  require  grinding- 
before  they  can  be  used,  and  in  many  cases  a  mixture  of  a  certain 
percentage  of  clay  to  bring  about  the  proper  degree  of  plasticity. 

By  the  proper  mixing  of  clays  possessing  different  degrees  of 
fusibility  and  refractoriness  a  combination  is  often  reached  that 


88  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

permits  the  utilization  of  a  great  number  of  clays  that  would 
otherwise  be  valueless  for  vitrified  products.  Perfectly  satisfactory 
clays  are  not  often  found  in  a  natural  state. 

Burned  or  dried  clay  has  been  in  use  as  pottery  or  bricks  for 
many  centuries.  Pottery  has  been  made  by  all  prehistoric  races, 
with  the  single  exception  of  the  cave-dwellers  of  the  Drift  period, 
from  the  Neolithic.  The  early  specimens  were  rudely  shaped  and 
made  by  hand,  but  appliances  for  forming  the  clay  were  gradually 
discovered,  and  the  Egyptians  were  known  to  have  used  potter's 
wheels  as  early  as  4000  B.C. 

Allusion  is  also  made  to  the  wheel  in  Jeremiah  xviii.  3,  4,  as 
well  as  in  several  places  in  Homer.  Fragments  of  pottery  have 
been  found  in  clay-brick  used  in  the  construction  of  the  oldest 
pyramid. 

Bricks  themselves  were  used  in  the  tower  of  Babel,  as  well  as 
in  the  walls  of  the  city  of  Babylon.  The  children  of  Israel  made 
bricks  of  clay  and  chopped  straw  during  their  captivity  in  Egypt 
under  Pharaoh.  These  were  probably  baked  in  the  sun,  although 
about  that  time  some  bricks  were  burned  by  the  Egyptians. 

Samples  of  enamelled  work  were  found  on  the  walls  of  the 
palace  of  Eameses  II.  built  about  140  B.C.  Bricks  were  also  ex- 
tensively used  in  the  palaces  of  Babylon  and  Nineveh  constructed 
some  two  hundred  years  later. 

Some  of  the  pyramids  were  made  of  bricks,  and  upon  one  of 
them  was  found  this  inscription: 

"  Do  not  undervalue  me  by  comparing  me  with  pyramids  of 
stone.  For  I  am  better  than  they,  as  Jove  exceeds  the  other 
deities.  I  am  made  of  bricks,  from  clay  brought  up  from  the  bot- 
tom of  the  lake  adhering  to  poles."  This  shows  that  even  at  that 
period  bricks  had  been  used  for  a  sufficient  time  to  demonstrate 
their  enduring  qualities. 

They  were  used  to  a  great  extent  by  the  ancient  Greeks  and 
Romans,  the  former  being  said  to  have  brought  them  to  perfec- 
tion. 

The  walls  and  temples  of  Athens,  as  well  as  the  palace  of 
Croesus,  were  constructed  wholly  or  in  part  of  brick,  though,  on 
account  of  stone  being  so  plentiful  in  Greece,  they  were  not  in  so 
great  a  demand  there  as  in  other  countries. 


BRICK-CLAJS—  MANUFACTURE  OF  PAVING-BRICK.        89 

Strabo  mentions  a  floating  brick  made  of  a  kind  of  silicious 
earth  that  when  burned  has  a  less  specific  gravity  than  water. 

M'odern  bricks  were  first  used  in  Suffolk,  England,  in  1260, 
though  they  were  not  manufactured  of  good  quality  until  about  one 
hundred  years  later.  They  did  not  come  into  general  use  in  London 
till  after  the  great  fire  in  1660. 

The  first  brick-kiln  in  this  country  was  probably  built  in  Salem, 
Mass.,  in  1629,  although  for  some  years  after  the  early  settlements 
nearly  all  of  the  bricks  used  here  were  brought  from  Holland  or 
England.  In  old  houses  in  Albany,  N.  Y.,  and  vicinity  some  of  the 
original  Dutch  bricks  can  still  be  found. 

The  manufacture  of  paving-bricks.is  of  very  recent  origin.  They 
were  first  used  in  this  country  as  paving  material  in  1870.  And  not 
for  some  time  after  that  did  brick-makers  realize  that  a  new  in- 
dustry had  been  opened  up  for  them.  But  in  1897  it  had  been 
developed  to  such  an  extent  that  in  that  year  there  were  manu- 
factured in  the  United  States  435,851,000  vitrified  bricks,  having  a 
value  of  $3,582,037.  Illinois  headed  the  list  of  States  with  87,169,- 
000,  closely  followed  by  Ohio  with  85,665,000. 

In  1898  the  production  was  462,499,000,  valued  at  $3,922,642, 
but  Ohio  had  displaced  Illinois  for  first  place  with  a  total  of  115,- 
104,000,  against  71,999,000  for  the  latter  State,  the  average  price 
per  thousand  being  $6.92  in  Ohio  and  $8.88  in  Illinois. 

A  peculiar  "  blue  brick,"  so  called,  is  made  for  paving  purposes 
in  Birmingham,  England.  The  material  used  is  a  very  ferruginous 
shale.  After  the  bricks  have  been  placed  in  a  kiln  the  heat  is  raised 
to  the  vitrification-point.  Salt  is  then  thrown  on  the  fire  and, 
being  volatilized  by  the  heat,  covers  the  bricks  with  a  thin  glaze. 
Fresh  coal  is  also  added  to  the  fire  at  the  same  time,  and  all  open- 
ings in  the  kiln  tightly  closed.  This  causes  a  reduction  in  the 
iron  near  the  surface  of  the  bricks  and  a  thorough  fusing  of  the 
particles  in  this  outer  crust.  The  process  makes  a  hard,  dense 
brick  with  the  outer  inch  or  half-inch  a  bluish  black,  while  the 
inner  portion  is  a  deep  red. 


90  STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

THE  MANUFACTURE  OF  PAVING-BRICK.* 
Crushing  the  Clay. 

Whether  clay  or  shale  is  used  for  paving-brick,  it  is  usually 
crushed  in  dry  pans,  or  mills  with  solid  rolls  that  are  about  4  feet 
in  diameter  and  12  inches  wide,  running  within  a  revolving  pan 
9  feet  in  diameter,  with  grated  bottom.  Two  such  pans  can  gen- 
erally supply  the  largest-sized  brick-machine,  as  they  each  crush 
from  5  to  10  cubic  yards  of  shale  per  hour.  It  requires  about  2 
cubic  yards  of  clay  for  one  thousand  brick. 

Screening. 

From  the  pans  the  crushed  material  goes  to  screens  with  both 
fixed  and  shaking  riddles.  They  require  the  use  of  knockers  to 
prevent  the  wet  clay  from  sticking,  and  at  some  plants  a  boy  is 
needed  to  keep  the  screens  from  clogging.  In  the  older  plants  the 
sizing  was  often  accomplished  by  the  grating  of  the  dry  pans,  no 
screens  being  employed.  This,  however,  is  a  mistake,  as  it  reduces 
the  capacity  bf  the  pan  and  causes  very  imperfect  crushing  from 
the  wear  and  breakage  of  the  bridges  to  the  gratings.  As  the  finer 
the  clay  is  crushed,  the  stronger  the  resulting  brick,  these  coarse 
particles  produce  an  inferior  non-homogeneous  product.  Most 
plants  are  still  faulty  in  not  screening  fine  enough,  as  4-  to  8-mesh 
screens  are  employed,  whereas  10  to  15  meshes  per  linear  inch 
should  be  used  to  give  the  best  results. 

Pugging. 

The  crushed  clay  or  shale  is  next  mixed  and  worked  with  water 
into  a  plastic  mass  by  the  pug-mill,  which  is  a  long  trough  contain- 
ing a  series  of  wide  blades  set  with  a  cross-pitch  on  a  heavy  shaft. 
This  pugging  should  be  thoroughly  done  to  remove  air-inclosures, 
secure  a  homogeneous  mixture,  and  reduce  the  laminations  in 
moulding  to  a  minimum.  To  accomplish  this,  the  mills  should  be 
at  least  10  or  12  feet  long  and  have  the  blades  or  knives  90  degrees 
apart.  Fire-clays  are  often  pugged  in  "  wet  pans  "  or  "  chasers," 
which  are  small  mills  with  a  solid  bottom,  while  the  rolls  have 

*  Somewhat  abridged  from  Wheeler's  "Vitrified  Paving- brick." 


BRICK  CLAT8— MANUFACTURE  OF  PAVING-BRICK.       91 

a  narrow  tread.  The  clay  is  both  crushed  and  tempered,  or  worked 
into  a  homogeneous  paste  in  this  pan,  being  kept  in  it  until  thor- 
oughly ground  and  tempered.  The  "  wet  pan  "  yields  a  product 
superior  to  that  of  the  pug-mill,  as  it  can  be  retained  indefinitely  in 
the  pan,  or  until  thoroughly  tempered;  but  as  it  requires  a  larger 
plant  and  takes  more  labor  and  power,  it  is  not  usually  used  for 
paving-brick. 

Moulding. 

'  Paving-brick  are  generally  made  by  the  stiff-mud  process,  but 
numerous  attempts  have  been  made  to  use  the  semi-dry  or  dry  press 
methods,  but  they  have  failed  to  produce  a  large  percentage  of 
good  pavers.  In  the  dry-press  systems  there  is  no  bond  between  the 
clay  particles  and  they  merely  cohere  as  a  result  of  the  quickly 
applied  pressure,  and  unless  such  brick  are  burned  to  complete 
vitrification  they  fail  to  give  a  solid,  strong,  non-porous  brick. 

The  type  of  machine  used  for  the  stiff-mu'd  process  is  usually 
a  continuous  working  auger  which  forces  the  tempered  clay  or  mud 
through  the  forming  die.  This  gives  a  continuous  bar  of  stiff  clay, 
which  is  placed  under  an  automatic  cutter  that  cuts  it  into  the 
desired  sizes.  As  the  bar  leaves  the  die  it  is  usually  sanded  to  pre- 
vent the  bricks  from  sticking  together  in  the  kiln.  Instead  of  an 
auger  producing  a  continuous  stream  of  clay,  reciprocating  plung- 
ers are  sometimes  employed  which  give  an  intermittent  bar,  and 
occasionally  steam-cylinders  with  dry  plungers  are  used  similar  to 
the  sewer-pipe  process.  The  first  method  is  the  cheapest,  and  this 
style  of  machine  has  been  developed  to  a  producing  capacity  of 
12,000  bricks  an  hour,  or  100,000  per  day. 

Formerly  dies  were  made  about  4£  x  2£  inches  in  size,  producing 
end-cut  brick,  but  of  late  9  x  4|-ineh  dies  are  being  used,  which 
give  a  side-cut  brick.  This  form  of  brick  is  more  shapely  and 
decidedly  preferable  for  a  building-brick  and  for  repressing,  but 
as  to  which  will  make  a  more  solid  brick,  a  brick  with  fewer  lamina- 
tions, will  have  to  be  settled  for  each  individual  clay.  The  weak 
point  of  the  stiff-mud  process  is  the  laminations  that  must  in- 
evitably result  from  pushing  the  stream  of  clay  through  a  fixed  die. 
The  friction  on  the  sides  of  the  die  will  cause  different  speed  in  the 
flow  of  the  clay,  and  these  variations  in  the  speed  of  the  outflowing 


92          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

clay  must  necessarily  result  in  laminations  or  lines  of  demarcation 
between  the  different  speeds  of  the  clay  bar  similar  to  the  veins  of 
a  glacier. 

If  the  air  has  been  expelled  from  the  clay  by  the  pug-mill, 
these  lines  can  be  largely  closed  up  again  by  a  properly  shaped  die,, 
and  first-class  brick  will  result  in  which  the  laminations  will  be 
inconspicuous  and  of  no  importance.  But  if  the  air  has  not  been 
expelled,  or  the  mill  and  die  are  not  properly  designed,  there  will 
be  an  excessive  amount  of  concentric  lines  that  almost  divide  the 
cross-section  of  the  brick  into  a  series  of  shells  or  concentric  cylin- 
ders that  greatly  weaken  the  brick  for  withstanding  blows  or  frost. 
The  character  of  the  clay  also  greatly  increases  these  laminations,, 
as  the  softer  it  is  tempered,  or  the  more  plastic  it  is,  the  more 
serious  is  this  trouble.  The  clay  should  be  worked  as  stiff  as  pos- 
sible, not  only  to  make  it  dense  and  reduce  the  shrinkage,  but  also 
to  reduce  the  laminations.  A  very  stiff  clay  requires  more  power 
to  work  it,  however,  and  if  too  stiff  is  very  apt  to  break  down  the 
machine. 

Repressing. 

Repressing  consists  in  putting  freshly  made  "stiff -mud  brick  into- 
a  die-box  and  momentarily  subjecting  it  to  a  heavy  vertical  pressure,, 
which  is  usually  applied  on  the  flat  side.  This  fills  out  the  angles 
and  edges,  making  a  much  more  shapely  and  uniform  brick  which 
is  slightly  denser,  but  probably  also  decreases  the  laminations? 

Drying. 

The  stiff -mud  brick  are  pilled  in  a  sort  of  checkerwork  on  cars- 
as  high  as  they  will  bear  their  own  weight,  some  six  or  eight  courses, 
high,  and  dried  in  long  tunnels  or  drying-chambers,  heated  by 
direct  fires,  steam-pipes,  or  hot  air.  On  account  of  the  marked 
difference  in  the  drying  properties  of  clay,  the  selection  and  design 
of  the  dryer  is  a  very  important  matter  and  it  must  be  adapted 
for  the  specific  clay  to  be  used.  Some  clays  can  be  readily  dried 
in  18  to  30  hours  without  checking  or  injuring,  while  others  need 
48  to  60  hours,  or  longer,  to  avoid  cracking  to  pieces.  This  means 
a  great  difference  in  the  drying  arrangement  and  expense  of  oper- 
ating the  drying  plant,  which  too  frequently  is  not  appreciated  by 


i 
BRICK  CLATS— MANUFACTURE  OF  PAVING-BRICK.       93 

the  brick-maker  or  enthusiastic  venders  of  patented  dryers,  and 
generally  results  in  an  expensive  drying  department. 

Burning. 

This  is  a  most  important  part  of  the  paving-brick  business,  as, 
no  matter  how  good  the  clay,  or  how  well  it  may  have  been  mixed, 
without  proper  burning  it  cannot  make  Xo.  1  paving-brick.  The 
kind  of  kiln  employed  in  burning  paving-brick  is  the  down-draft 
rather  than  the  round  or  oblong,  as  the  up-draft  type  produces  too 
heavy  a  percentage  of  soft  and  overburned  brick.  A  continuous 
kiln  has  also  been  tried  on  paving-brick,  but  has  not  been  very  suc- 
cessful. The  improvements  that  have  been  made,  however,  would 
seem  to  indicate  that  this  type  might  at  some  time  be  used. 

It  is  interesting  to  note  the  changes  that  occur  in  paving-clays 
in  passing  from  the  condition  of  mud  to  a  first-class  paving-brick. 
When  the  moulded  brick  go  into  the  dryer  and  the  mechanically 
mixed  water  is  evaporated,  the  brick  shrink  from  2  to  11  per  cent 
to  a  firm  earthy  mass  that  admits  handling  and  in  which  the  in- 
dividual particles  of  clay  are  plainly  distinguished.  On  being 
'heated  to  a  red  heat,  or  about  1200°  Fahr.,  the  chemically  com- 
bined water  is  driven  off,  which  renders  the  clay  non-plastic  and  it 
again  begins  to  shrink  and  to  grow  harder  and  stronger.  As  the 
heat  is  raised  above  redness,  the  individual  particles  of  clay  may  be 
still  easily  recognized  and  the  brick  are  very  porous.  When  the 
heat  is  still  further  raised  to  about  a  bright  cherry  heat  or  from 
1500°  to  1800°  Fahr.,  depending  on  the  particular  clay,  it  shrinks 
an  additional  1  to  10  per  cent  and  is  very  much  stronger  and  much 
less  porous.  It  has  the  acquired  hardness  of  tempered  steel  and  the 
individual  particles  are  no  longer  recognizable.  This  is  the  be- 
ginning of  vitrification.  From  this  stage  to  the  molten  mass  there 
is  no  longer  any  sharp  line  of  demarcation,  and  as  the  heat  is  in- 
creased the  brick  finally  become  viscous  and  semi-liquid,  and  when 
chilled  and  broken  present  a  thoroughly  glassy  appearance. 

From  the  point  at  which  the  clay  particles  have  so  coalesced 
that  they  can  be  no  longer  recognized  to  the  point  of  viscous 
liquidity  requires  an  increase  in  temperature  of  100°  to  600°  Fahr., 
according  to  the  kind  of  clay,  and  is  usually  400°  in  a  clay  suitable 
for  paving-brick.  Midway  between  these  two  points  the  clay 


94:          STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

ceases  to  be  porous  and  stops  shrinking,  which  is  the  maximum 
degree  of  hardness  and  toughness,  and  is  the  point  at  which  the 
burning  should  be  stopped  in  order  to  produce  an  ideal  paving- 
brick. 

The  burning  usually  takes  from  7  to  10  days,  a  shale  brick  re- 
quiring from  1500°  to  2000°  Fahr.,  and  those  of  fire-clay  from 
1800°  to  2300°  Fahr.  If  shale  brick  are  heated  too  hot,  they  melt 
into  a  more  or  less  solid  mass,  yet  it  is  usually  necessary  to  bring 
them  to  a  heat  which  would  cause  them  to  stick  together  if  not 
prevented  by  sand  that  is  freely  sprinkled  between  them  in  setting. 
At  the  temperature  when  they  border  on  the  condition  of  a  very 
viscous  fluidity,  the  lower  brick  become  "  kiln-marked "  by  the 
weight  of  the  upper  bricks  forcing  the  lower  bricks  slightly  into 
one  another,  and  care  is  required  to  prevent  this  pressure  from 
becoming  too  great  by  not  setting  them  too  high.  Paving-brick 
are  set  only  22  to  34  courses  high,  according  to  the  fusibility  of 
the  clay.  Coal  is  used  throughout  in  burning  pavers,  which  do  not 
need  the  preliminary  or  water-soaking  stage.  Oil  and  natural  gas 
however,  'have  been  used  in  some  localities  and  are  far  superior 
to  coal  in  reducing  labor  in  burning,  and  producing  a  superior 
quality  of  brick,  from  the  uniformity  of  the  fire  and  avoidance  of 
the  air-checks  that  result  from  chills  when  cleaning  the  grate- 
bars. 

Annealing. 

After  the  kiln  has  been  maintained  long  enough  at  the  vitrify- 
ing temperature  to  heat  the  bricks  through  the  centre,  the  kiln 
should  be  tightly  closed  and  allowed  to  cool  very  slowly.  Slow 
cooling  is  the  secret  of  toughness,  and  the  slower  the  cooling  the 
tougher  the  brick.  This  annealing  stage  is  often  curtailed,  on 
account  of  insufficient  kiln  capacity,  and  the  kiln  cooled  down  in 
3  to  5  days  in  order  to  hurry  up  the  brick,  often  to  removing  bricks 
that  are  so  hot  as  to  set  fire  to  trucks.  At  least  7  to  10  days  should 
be  allowed  for  cooling  to  secure  tough  brick,  and  those  who  desire 
the  best  article  can  well  afford  to  pay  the  extra  cast  of  still  slower 
cooling  if  quality  is  the  first  consideration. 


BRICK  CLAYS— MANUFACTURE  OF  PAVING-BRICK.       95 

Sorting. 

If  the  kiln  is  properly  burned,  it  will  be  found  to  have  from 

1  to  4  courses,  the  top  brick,  that  are  burned  extremely  hard,  and 
which  are  more  or  less  air-checked  by  being  struck  by  cold  air  in 
coaling  or  cleaning  the  fires.     The  top  course  is  also  more  or  less 
covered  with  a  film  of  ashes  and  dust  that  has  been  carried  over 
by  the  draft.     Such  bricks  are  excellent  for  sewer  or  foundation 
work,  as  they  have  the  maximum  resistance  to  crushing  strength 
and  minimum  porosity.    Beneath  the  top  layer  the  brick  to  within 

2  to  12  courses  of  the  bottom  are  No.  1  pavers,  or  brick  that  should 
be  perfectly  sound,  completely  vitrified,  and  have  the  maximum 
strength,  hardness,  and  toughness.     Beneath   these  are  2  to   10 
courses  of  brick  which  'have  not  received  sufficient  heat  to  com- 
pletely vitrify  them  and  which  are  classed  as  No.  2  pavers,  and 
used  as  the  foundation  or  the  flat  courses  in  paving.    Beneath  the 
No.  2  pavers  are  from  1  to  6  courses  of  brick  which  have  not  re- 
ceived heat  enough  to  be  able  to  withstand  the  frost  and  are  called 
builders,  as  they  are  about  equivalent  in  strength,  hardness,  and 
porosity  to  the  hard-burned  building-brick. 

With  a  fire-clay  it  is  possible  to  produce  90  per  cent  of  No.  1 
pavers,  as  there  is  no  risk  from  overfiring  them,  while  80  per  cent 
is  a  high  average  for  shale.  One  frequently  sees  claims  by  venders 
of  patented  kilns  of  90  per  cent  of  No.  1  pavers,  but  such  a  very 
high  percentage  is  rarely  attained  with  careful  grading,  while  80 
per  cent  is  a  high  yield,  and  most  yards  do  not  get  as  high  as  70 
per  cent  of  strictly  first-class  No.  1  pavers. 


CHAPTER  V. 

CEMENT,    CEMENT    MORTAR,    AND    CONCRETE. 

WHEN  a  pure  limestone  has  been  properly  burned  or  calcined 
the  result  is  lime,  that  is,  the  carbonic  acid  has  been  driven  off  by 
the  action  of  the  heat.  When  water  is  applied  to  the  lime  it  slakes 
with  a  great  increase  in  volume,  and  if  more  be  added  it  can  be 
formed  into  a  paste,  which  when  mixed  with  sand  will  harden  or 
set  if  exposed  to  the  air. 

Limestone,  however,  is  very  seldom  found  in  a  pure  state,  the 
principal  impurities  generally  being  silica,  alumina,  iron,  and  mag- 
nesia. When  these  impurities  exceed  10  per  cent  the  resulting  lime 
has  the  property  of  setting  under  water  and  is  said  to  be  "  hy- 
draulic." If,  however,  the  rock  contains  about  40  per  cent  of  silica 
and  alumina,  the  product  of  the  calcination  will  not  slake  upon 
the  application  of  water,  but  must  be  reduced  to  a  powder  in  mills, 
when  it  is  made  into  a  paste  as  with  the  lime.  This  product  is 
known  as  "  cement."  It  differs  from  lime  physically  in  that  it  re- 
quires to  be  reduced  to  a  powder  before  being  used,  and  does  not 
materially  increase  its  volume  in  setting. 

Cements  were  known  to  and  largely  used  by  the  Romans,  and 
it  is  said  that  the  workmen  excavating  in  London,  England,  in  1892 
found  a  natural-cement  concrete  which  was  known  to  have  been 
laid  eight  hundred  years  before.  During  the  middle  ages  there 
seems  to  have  been  little  knowledge  of  limes  and  cements,  as  what 
is  known  at  present  dates  back  to  the  time  when  John  Smeaton, 
in  seeking  for  a»  mortar  wijth  which  to  construct  the  Eddystone 
lighthouse,  discovered  the  hydraulic  character  of  certain  limestones, 
and  that  this  property  was  caused  by  the  presence  of  clay  in  the 
original  rock. 

Cements  are  generally  spoken  of  in  this  country  as  "  natural " 

96 


CEMENT,  CEMENT  MORTAR,  AND   CONCRETE.  97 

or  "  artificial."  The  former,  as  the  name  implies,  is  made  from 
the  natural  rock,  while  the  latter  is  an  artificial  mixture,  the  in- 
gredients being  so  proportioned  as  to  bring  about  the  best  results. 
As  might  be  expected,  the  latter  are  stronger,  more  durable,  and 
much  more  expensive.  Artificial  cements  are  also  known  as 
•'  Portlands  "  from  the  fact  that  they  were  first  manufactured  in 
England,  and  that  when  set  they  bore  a  strong  resemblance  to  the 
natural  stone  found  in  the  island  of  Portland.  In  a  very  few  locali- 
ties limestone  has  been  found  which  when  burned  has  almost  the 
same  composition  as  the  artificial  Portlands.  On  account  of  this 
similarity  these  have  been  called  "  natural  Portlands."  A  cement 
of  this  character  was  produced  in  France  in  1802.  Portland  cement 
as  known  at  the  present  time  was  first  manufactured  in  England 
in  about  1824,  although  patents  for  "  Portland  cements  "  had  been 
issued  several  years  previously. 

The  following  is  the  description  given  by  the  patentee  in  the 
first  specifications  issued: 

"  I  take  a  specific  quantity  of  limestone  and  calcine  it.  I 
then  take  a  specific  quantity  of  clay  and  mix  it  with  water  to  a 
state  approaching  impalpability.  After  this  proceeding  I  put  the 
above  mixture  into  a  slip-pan  for  evaporation  till  the  water  is  en- 
.  tirely  evaporated.  Then  I  break  the  said  mixture  into  suitable 
lumps  and  calcine  them  in  a  furnace  similar  to  a  lime-kiln  until  the 
carbonic  acid  is  entirely  expelled.  The  mixture  so  calcined  is  to  be 
ground  to  a  fine  powder,  and  it  is  then  in  a  fit  state  for  cementing. 
The  powder  is  to  be  mixed  with  a  sufficient  quantity  of  water  to 
bring  it  into  the  consistency  of  mortar,  and  this  applied  to  the 
purposes  wanted." 

In  1796  a  Mr.  Parker  of  London  patented  a  process  of  making 
a  "  Roman  "  cement.  This  was  so  called,  and  properly,  on  account 
of  the  similarity  to  the  cement  in  use  by  the  Romans  so  many 
years  before. 

In  this  country  a  cement  similar  to  the  above  was  manufactured 
at  Fayetteville,  N.  Y.,  in  1818. 

Portland  cement  was  first  produced  in  the  United  States  in 
1865.  At  the  present  time  the  principal  works  are  situated  in 
Pennsylvania,  Ohio,  New  York,  and  one  in  South  Dakota. 


98  STREET  PAVEMENTS  AND  PAYING  MATERIALS. 

In  1828  a  natural-cement  rock  was  discovered  at  Rosendale, 
New  York,  and  afterwards  similar  formations  in  other  portions 
which,  on  account  of  the  similarity,  were  also  called  "  Rosendales," 
being  distinguishable  from  each  other  by  a  special  name  for  each 
brand.  As  the  country  was  settled  and  construction  work  was 
undertaken  in  other  sections,  more  deposits  were  found,  a  notable 
one  near  Louisville,  Ky.,  and  now  some  authorities  call  all  natural 
cements  "  Rosendales,"  to  separate  them  from  the  "  Portlands." 

In  the  new  Building  Code  recently  adopted  by  the  city  of  New 
York  the  following  is  found  in  relation  to  Portland  and  other 
cements: 

"  Cements  classed  as  Portland  shall  be  considered  to  mean  such 
cement  as  will,  when  tested  neat,  after  one  day  set  in  air  be  capable 
of  sustaining  without  rupture  a  tensile  strain  of  at  least  120 
pounds  per  square  inch,  and  after  one  day  in  air  and  six  days  in 
water  be  capable  of  sustaining  without  rupture  a  tensile  strain  of  at 
least  300  pounds  per  square  inch.  Cements  other  than  Portland 
cement  shall  be  considered  to  mean  such  cement  as  will,  when 
tested  neat,  after  one  day  set  in  air  be  capable  of  sustaining  with- 
out rupture  a  tensile  strain  of  at  least  60  pounds  per  square  inch, 
and  after  one  day  in  air  and  six  days  in  water  be  capable  of 
sustaining  without  rupture  a  tensile  strain  of  at  least  120  pounds 
per  square  inch.  Said  tests  are  to  be  made  under  the  supervision 
of  the  Commissioner  of  Buildings  having  jurisdiction,  at  such  times 
as  he  may  determine,  and  a  record  of  all  cements  answering  the 
above  requirements  shall  be  kept  for  public  information." 

It  will  be  seen  by  the  above  that  the  cement  is  graded  by  its 
strength.  This  standard  is,  perhaps,  as  satisfactory  as  any,  if  the 
tests  are  carried  on  for  a  sufficient  length  of  time,  but  most 
engineers  would  hesitate  to  accept  or  reject  cements  of  which  they 
knew  nothing,  from  the  result  of  so  short  a  time-test  as  seven  days. 
Under  this  clause  no  cements  can  be  used  that  develop  a  strength 
of  less  than  60  pounds  in  one  day  set  in  air. 

Natural  and  Portland  cements  can  be  readily  distinguished, 
however,  by  their  composition. 

Table  No.  14  is  made  up  from  analyses  of  well-known  cements 
and  taken  from  Cumming's  "  American  Cements." 


CEMENT,  CEMENT  MORTAR,  AND   CONCRETE. 


TABLE  Xo.  14. 

PORTLAND   CEMENTS. 


Brand. 

ej 
«j 

OQ 

Alumina. 

Q 

!2 

X 

C 

j 

Magnesia. 

Potash  and 
Soda. 

is 

f3 

Carbonic  Acid, 
Water,  and 
Undetermined. 

K    B   &  S  

19.75 

7.48 

5.01 

60.71 

1.28 

0.75 

1.64 

3  38 

24.90 

8.00 

3.22 

59.38 

0.38 

0.50 

1.46 

2  16 

19  35 

7  00 

4  50 

63  75 

5  40 

Gerinania  

21.14 

6  30 

2.50 

66.04 

1.11 

2  91 

22.91 

8  00 

1.90 

61.76 

2.70 

2  63 

Giant  

23.36 

8  07 

4.83 

58.93 

1.00 

0.50 

0  85 

2  46 

Alpha  

22.89 

8.00 

2.44 

63.38 

2.30 

0  99 

Natural,       Boulogne, 
France  

20.42 

12.00 

1.87 

63.13 

0.58 





2.00 

Average  

21.84 

8.11 

3.28 

62.12 

1.17 

2.74 

Mr.  Launcelot  Andrews,  Ph.D.,  in  an  article  on  cements  in 
Clay  Record  says  that  an  ideal  Portland  cement  should  be  com- 
posed of: 

Per  cent. 

Lime 62.2 

Silica  28.2 

Alumina  9.6 

but  adds  that  about  a  third  of  the  alumina  may  be  replaced  by ' 
ferric  oxide,  which  would  correspond  to  the  composition: 

Per  cent. 

Lime 61.7 

Silica  " 27.4 

Alumina  7.5 

Ferric  oxide   3.4 

He  also  gives  3  per  cent  of  magnesia  as  the  maximum  to  be 
allowed,  a  larger  amount  having  a  tendency  to  cause  the  cement  to 
swell  and  crumble. 

Table  No.  15  shows  the  composition  of  several  well-known 
American  cements,  also  taken  from  Cumming's  "  American  Ce- 
ments." 


100        STEEET  PAVEMENTS  AND  PAVING  MATERIALS. 


TABLE  Xo.  15. 

NATURAL   CEMENTS. 


Brand. 

I 

p 

a 

j3 

Iron  Oxide. 

§ 

3 

1 

•a 
a 

03 
1* 

jll 

Utica  

34.66 

5.10 

.00 

30.24 

18.00 

6.16 

4.84 

23.16 

6.33 

.71 

36.08 

20.38 

5.27 

7.07 

Louisville,  "  Four  Leaf  "  .  . 
Louisville,  "  Hulme  Star".. 

26.40 
25.28 
27.30 

6.28 

7.85 
7.14 

.00 
.43 

.80 

45.22 
44.65 
35.98 

9.00 
9.50 
18.00 

4.24 
4.25 
6.80 

7.86 
7.04 
2.98 

Norton    High  Falls  ... 

27.98 

7.28 

.70 

37.59 

15.00 

7.96 

2.49 

28.43 

6.71 

.94 

36.31 

23.89 

1.80 

0.92 

27.60 

6.67 

1.51 

38.01 

16.25 

5.21 

4.74 

It  will  be  noticed  that  the  two  brands  of  Louisville  very  quick- 
setting  cements  are  high  in  lime  and  correspondingly  low  in  mag- 
nesia, that  there  is  a  difference  between  the  naturals  and  Portlands 
in  every  essential  ingredient,  and  that  it  is  so  marked  that  the  one 
can  always  be  distinguished  from  the  other. 

Fineness. 

Besides  its  composition,  there  is  another  property  of  cement 
which  has  an  important  bearing  upon  its  value  in  mortar,  and  that 
is  its  fineness.  It  costs  materially  more  to  grind  a  cement  so  that 
75  per  cent  of  it  will  pass  a  sieve  of  40,000  meshes  per  square  inch 
than  to  pass  one  of  10,000,  so  that  the  tendency  is  to  leave  the 
product  as  coarse  as  possible  and  get  ,satisf  actory  results.  Gillmore 
says:  "The  capacity  of  a  cement  to  receive  sand,  other  things 
being  equal,  varies  directly  with  its  degree  of  fineness."  As 
cements  are  always  used  in  practice  mixed  with  a  certain  amount 
of  sand,  this  matter  is  of  great  importance.  The  author  just 
quoted  says  that  not  more  than  8  per  cent  of  a  cement  should  be 
rejected  by  a  sieve  of  6400  meshes  to  the  square  inch.  Mr. 
Andrews,  previously  referred  to,  says  that  all  grains  so  large  as  not 
to  pass  a  sieve  of  75  meshes  to  the  linear  inch  (5625  per  square  inch) 
should  be  considered  as  inert  or  wholly  passive  constituents,  and 


CEMENT,  CEMENT  MORTAR,  AND   CONCRETE. 


101 


that  they  should  not  constitute  more  than  20  per  cent  of  the  total 
weight. 

Mr.  E.  W.  Lesley  in  examining  different  specifications  upon 
this  point  found  the  requirements  as  shown  in  Table  No.  16  (the 
results  being  given  in  a  paper  read  before  the  Engineers'  Club  of 
Philadelphia). 

TABLE  No.  16. 

PORTLAND   CEMENTS. 


Brand. 

Percentages  to  pass  Screens  of  the  following 
Meshes  per  Square  Inch. 

2500 

3GOO 

6400 

8000 

10000 

40000 

U.  S.  Army  

954 
95 

84 

70 

U.  S   Navy  .    .            

97 

90 

District  of  Columbia    

95 
97 
95£ 
97 

85 
89 

69 

Six  street  and  steam  railways  

80 

A  number  of  bridge  companies  
Average  of  71  specifications  

96 

A.N  CKS 

85 

69 

AMEKIC 

IENTS. 

Average  of   38    American  specifica- 

92 

85 

79 

U.  S.  Army  

91 

85 

724 

«*Tf 

In  prosecuting  the  Boston  Main  Drainage  Works,  Mr.  Eliot  C. 
Clarke  made  some  very  elaborate  experiments  to 'show  the  effect 
of  fine  grinding  on  cements.  In  Tables  Nos.  17  and  18  are  given 
some  of  his  results.  The  figures  represent  the  tensile  strength  in 
pounds  per  square  inch. 

In  Table  No.  18  the  same  brand  was  used  in  both  cases,  but 
one  sample  was  taken  from  the  ordinary  delivery,  and  the  other 
from  a  lot  that  had  been  ground  in  accordance  with  a  special  con* 
tract. 

Another  test  was  made  by  taking  the  average  of  these  brands 
of  finely  ground  with  the  same  number  more  coarsely  ground,  with 
the  results  shown  in  Table  No.  19. 

These  tables  show  conclusively  the  value  of  fine  grinding,  and, 
as  far  as  investigations  have  been  carried,  that  the  finer  the  cement 


102        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

TABLE  No.  17. 


Brand. 

Age  of 
Specimen. 

Percentage 
retained 
on  a  No.  120 
Sieve. 

Parts  of  Sand  to  one  part  of  Cement. 

0 

2 

3 

4 

5 

43 

86 

English  Portland.  .  .  . 
French  Portland.   .  .  . 

7  days 
do. 

37 
13 

319 

318 

125 
205 

89 
130 

59 
114 

TABLE  No.  18. 


Parts  of  Sand  to  one  part  of 

Brand. 

Age  of 
Specimen. 

Percentage 
retained  on  a 
No.  120  Sieve. 

Cement. 

0 

3 

5 

Ordinary  Portland  

28  days 

35 

403 

105 

68 

Finely  ground  Portland 

28  days 

12 

304 

180 

96 

TABLE  No.  19. 


Brand. 

Age  of 
Specimen. 

Percentage 
retained  on  a 
No.  50  Sieve. 

Parts  of  Sand  to  one  part  of 
Cement. 

0 

IX 

2 

16 
25 

Coarse  Kosendale  .  .    . 

7  days 
7  days 

17 
6 

98 
92 

29 
41 

Fine  Rosendale     .   .  . 

is  ground  the  more  strength  it  will  have  when  mixed  with  sand. 
On  account  of  the  great  cost  of  extreme  grinding,  it  is  not  economi- 
cal to  carry  it  too  far.  From  the  figures  previously  given,  it  would 
seem  that  the  authorities  had  decided  upon  a  sieve  of  200  meshes 
to  the  linear  inch  as  the  limit  to  be  required. 

Concerning  the  tests  to  be  made  of  cements  to  determine  its 
real  value  or  its  special  fitness  for  any  particular  work,  there  is 
much  to  be  said.  Different  engineers  have  different  requirements 
when  seeking  for  the  same  results,  and  different  laboratories  differ 
very  much  among  themselves  in  their  methods,  and  consequently 
their  results  vary  materially  even  when  cement  from  the  same 
barrel  is  used.  The  best  illustration  of  this  is  shown  in  Table 


CEMENT,   CEMENT  MORTAR,  AND   CONCRETE. 


103 


Ko.  20,  taken  from  a  paper  by  Prof.  J.  M.  Porter  of  Lafayette 
College.  Prof.  Porter  had  ten  samples  taken  from  the  same  num- 
ber of  barrels  of  Portland  cement,  thoroughly  mixed,  and  then 
divided  into  ten  smaller  portions  which  were  sent  to  ten  different 
persons  with  a  request  that  a  seven-day  tensile  test,  one  cement 
to  three  sand,  be  made  according  to  the  standard  of  the  American 
Society  of  Civil  Engineers. 

TABLE  No.  20. 


Tensile  Strength  in  Pounds. 

Range  in 
Pounds. 

Ratio  of 
Range  to 
Maximum. 

Ratio  of 
Average  to 
Last. 

Water,per  ct. 

1 

2 

3 

4 

5 

6 

:  ;i 
153 

Aver- 
age. 

75 
102 

114 
133 
140 
153 

163 

176 

225 
247 

R.  W.  Hildreth  &  Co.,  New  York.. 
Prof.  J.  B.  Johnson,  Washington 
University,  St.  Louis  
H.     R.     Fahr,     City     Engineer, 
Easton,  Pa  
Prof.  W.  H.  Burr,  Columbia  Col-  ( 
lege,  New  York  { 
Chas.  F.  McKenna,  New  York  
Prof.  F.  P.  Spalding,  Cornell  Uni- 
versity Ithaca  ...                  .... 

68 
77 

106 
125 
126 
148 

155 

171 
220 
240 

72 

94 

112 
126 
132 
150 

160 

177 
224 
246 

74 

108 

123 
130 
138 
151 

164 

177 
226 
249 

78 
110 

82 
122 

14 
45 

17 
19 
27 
12 

17 

8 
8 
12 

17.1 
36.9 

13.8 
13.2 
17.7 
7.5 

9.9 

4.5 
3.5 
4.8 

30.4 
41.8 

46.5 
54.0 
56.8 
62.0 

66.0 

71.4 
91.2 
100 

13 

Not 
given 

10.4 
10 
8 
12 
Not 
given 

11 
10 
12 

10.8 

137 
144 
155 

166 

178 
228 
250 

140 
150 
160 

172 
179 

o.JS 

252 

Prof.  J.  N.  Porter,  Lafayette  Col- 
lege, Easton  
Clifford  Richardson.  Washington. 
Booth  Garrett  &  Blair,  Phila  

Average 

153  117.9 

12.9 

62.0 

These  results  would  seem  to  indicate  that  such  tests  are  of  little 
value  when  a  report  from  one  laboratory  would  cause  the  cement 
to  be  rejected  without  hesitation  under  ordinary  specifications,  and 
as  unhesitatingly  accepted  according  to  the  report  of  another 
equally  reliable,  and  when  a  special  effort  has  been  made  to  have 
all  conditions  as  nearly  alike  as  possible.  This  is  hard  to  explain. 
But  on  account  of  these  variations  tests  of  cement  must  not  be 
given  up,  but  continued  with  more  care,  and  perhaps  on  different 
lines. 

It  is  rarely  possible  to  give  the  cement  used  in  any  large  and 
important  work  sufficient  tests  to  demonstrate  its  absolute  fitness. 
It  must  be  done  analogically.  It  is  necessary,  however,  to  fin-1  a 
brand  of  cement  before  the  work  is  begun  that  either  by  experience 
or  long-time  tests  has  been  proved  to  be  all  that  is  required.  If  the 
former,  a  series  of  tests  should  be  made  extending  over  a  sufficient 


104        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

period  of  time  and  comprising  enough  individual  samples  of  the 
cement  to  establish  a  rigid  standard  for  that  particular  brand.  It 
should  include  neat  tests  and  also  those  mixed  with  every  propor- 
tion of  sand  that  is  liable  to  be  used  on  the  work,  to  ascertain  as 
well  what  mixture  of  sand  will  produce  the  requisite  strength. 
During  construction  work  cement  is  liable  to  be  delivered  in  such 
quantities  that  it  is  not  possible  to  make  long-time  tests  without 
working  a  hardship  on  the  contractor.  If,  however,  a  standard  has 
been  established,  and  it  is  definitely  known  that  a  certain  strength 
neat  in  seven  days  will  develop  into  a  certain  other  strength  in 
thirty  or  ninety  days  mixed  with  the  specified  amount  of  sand,  a 
very  accurate  and  satisfactory  conclusion  can  be  arrived  at.  Each 
cement,  however,  must  have  its  own  standard,  and  the  operator  who 
makes  the  original  tests  should  be  retained  to  carry  them  on 
during  the  prosecution  of  the  work. 

No  new  cement  should  be  accepted  on  short-time  tests.  They 
are  often  very  deceptive.  Unless  it  has  been  used  and  gained  a 
reputation,  careful  and  elaborate  tests  should  be  made  as  detailed 
above.  The  briquettes  should  be  mixed  neat  and  with  the  propor- 
tions of  sand  determined  upon,  the  same  day  and  by  the  same  per- 
son, using  the  same  sample  of  cement  for  both  neat  and  sand 
briquettes,  so  that  the  loss  of  strength  occasioned  by  the  added  sand 
can  be  accurately  determined.  Long-time  tests  are  absolutely  nec- 
essary, as  a  few  cements  with  a  moderate  amount  of  sand  will  give 
practically  as  great  a  strength  as  when  tested  neat.  As  it  is  long- 
time results  that  are  desired  in  construction,  the  importance  of  this 
can  be  readily  seen.  Table  No.  21  clearly  illustrates  this. 


TABLE  No.  21. 


Age  of  Specimen. 

Neat. 

One  Part  Cement, 
Two  Parts  Sand. 

24  hours 

40 

7  days 

107 

46 

28  days 

'      254 

162 

2  months 

346 

245 

3  months 

388 

311 

6  months 

450 

436 

CEMENT,  CEMENT  MORTAR,  AND   CONCRETE. 


105 


The  above  is  the  average  of  five  briquettes,  and  the  cement  is  a 
natural  product  well  known  in  the  New  York  market.  Thirty  per 
cent  of  water  was  used  in  the  neat  mixture  and  14  per  cent  in  the 
sand. 

Mr.  E.  B.  Noyes,  in  Journal  of  Engineering  Societies  for  June 
1896,  gives  a  case  in  point;  when  a  good  cement  was  rejected  and  a 
poorer  one  accepted  on  comparatively  short-time  tests  without 
apparently  any  previous  knowledge.  Table  No.  22  gives  his 
results. 

TABLE  No.  22. 


7  Days. 

28  Days. 

6  Months. 

12  Months. 

1 

19 

41 

210 

518 

2 

12 

24 

136 

530 

3 

42 

115 

202 

334 

4 

71 

182 

283 

260 

The  cement  was  an  American  brand,  and  the  briquettes  were 
mixed  one  part  cement  to  one  part  of  sand.  Nos.  1  and  2  were  not 
used  on  account  of  their  poor  showing  in  their  first  tests,  while  at 
the  end  of  the  year  their  superiority  was  clearly  demonstrated. 
No.  2  was  certainly  a  remarkable  specimen,  and  any  engineer  would 
be  justified  in  rejecting  it  upon  the  six  months'  test  without  having 
had  any  previous  knowledge  of  its  wonderful  recuperative  powers. 
In  many  works,  too,  it  could  not  be  used  notwithstanding  its  great 
strength  in  one  year,  as  its  development  during  the  first  six  months 
is  very  slow.  Sample  No.  4  actually  receded  in  strength,  though 
so  little  that  it  might  have  been  caused  by  some  individual 
briquette.  It  would  seem  to  be  a  fair  inference  that  it  had  practi- 
cally reached  its  limit  in  six  months. 

The  author  several  years  ago  had  some  tests  made  of  the  princi- 
pal American]  cements  tributary  to  the  city  where  he  was  then 
located,  practically  on  the  lines  as  indicated  above.  The  results 
were  very  satisfactory,  demonstrating  the  necessity  of  such  action, 
and  in  this  particular  case  bearing  out  some  action  that  had  been 
taken  in  rejecting  certain  cements.  Table  No.  23  gives  the  results 
att-iined. 


106        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


TABLE  No.  23. 

CEMENT   MIXED   NEAT. 
Briquettes  2  hours  in  air,  remainder  in  water. 


24  Hours. 

7  Days. 

15  Days. 

30  Days. 

90  Days. 

6  Months. 

9  Months. 

1  Year. 

1 

109 

112 

145 

155 

250 

241 

289 

227 

2 

214 

228 

219 

325 

387 

366 

421 

316 

3 

114 

186 

293 

290 

282 

291 

347 

339 

4 

87 

197 

^37 

264 

267 

220 

367 

288 

5 

46 

131 

1!>9     279 

298 

322 

402 

410 

6 

206 

248 

348  I   348 

334 

355 

372 

402 

CEMENT    1    PART,    SAND   2   PARTS,    REMAINDER   IN   WATER. 
Briquettes  1  day  in  air. 


1 

35 

80 

167 

216 

199 

197 

229 

9, 

40 

79 

122 

143 

155 

112 

161 

3 

38 

70 

114 

75 

89 

89 

82 

4 
5 



74 
26 

99 
53 

134 
95 

140 
141 

146 
153 

153 
145 

137 
142 

6 

81 

103 

138 

106 

81 

69 

84 

This  shows  that  No.  1,  which  was  the  weakest  at  the  end  of  a 
year  neat,  was  the  strongest  when  mixed  as  it  is  generally  used; 
and  that  Nos.  3  and  5,  which  were  two  of  the  'highest  neat,  were 
but  one-half  the  average  strength  of  the  other  at  the  end  of  the 
year  when  mixed  with  sand. 

Some  engineers  in  making  cement  specifications  go  very  elabo- 
rately into  the  component  parts  of  the  material,  exacting  a  certain 
percentage  of  one  substance  and  ruling  out  more  than  a  certain 
amount  of  another.  This  practice  is  dangerous,  unless  one  is  per- 
fectly sure  of  his  standing,  or  the  limits  are  so  elastic  as  to  be  of 
no  value.  It  is  really  encroaching  on  the  prerogative  of  the  manu- 
facturer. The  engineer  wishes  results,  and  it  is  the  maker's  busi- 
ness to  produce  a  cement  that  will  give  them.  The  manufacturer 
will  have  no  difficulty  in  meeting  any  requirements,  but  at  what 
cost  to  the  long-time  test  he  alone  might  be  able  to  tell.  Then  the 
products  of  different  mills  differ  so  that  a  slight  excess  of  one 
ingredient  might  be  neutralized  by  that  of  another.  It  is  well 
known  that  many  excellent  brands  of  cement  are  made.  It  is 
better  to  obtain  a  perfect  knowledge  of  the  peculiarities  of  each 


CEMENT,   CEMENT  MORTAR,  AND    CONCRETE. 


107 


and,  after  specifying  certain  of  these,  make  sure  that  each  delivery 
is  kept  up  to  the  standard. 

In  the  case  of  an  excessive  demand  when  the  output  is  small, 
manufacturers  are  liable  to  put  on  the  market  a  product  that  in 
the  rush  has  not  received  sufficient  attention,  and  which  ordinarily 
would  not  be  sent  forth — or  it  may  happen  without  their  knowl- 
edge. It  is  the  object  of  the  tests  to  detect  this  or  similar  defects 
in  standard  brands. 

In  the  paper  by  Mr.  Lesley  previously  referred  to,  he  gives  the 
requirements  for  tensile  strength  as  found  in  different  specifications 
and  shown  in  Table  No.  24. 

TABLE  No.  24. 

PORTLAND  CEMENTS. 


• 

24  Hours 

Neat. 

7  Days. 

28  Days. 

Neat. 

1  to  3. 

Neat. 

ItoS. 

U.  S    Army    

131 

402 
383 
462 
388 
319 

384 

119 
85 

547 

600 

189 

U   S   Navy. 

Cit>  specifications  

161 
115 

134 

134 

538 
483 

529 

201 

Railroads  

Average  of  a  number  of  specifi- 

118 

189 

NATURAL  CEMENTS. 


•  '  j  Hours 

7D 

ays. 

28D 

ays. 

Neat. 

Neat. 

1  to  2. 

Neat. 

1  to  2. 

U.  S.  Army  

40-70 

90-125 

25-50 

100-200 

65-200 

City  specifications     

50-100 

100-200 

150-300 

Cement  specifications  generally  specify  a  time  within  certain 
limits  for  the  initial  and  final  sets.  When  this  is  done,  and  in 
fact  the  time  of  setting  is  generally  noted  in  all  tests,  it  is  neces- 
sary to  define  what  is  meant  by  these  terms.  A  standard  was  first 
adopted  by  General  Totten  at  his  work  at  Fort  Adams,  R.  I.,  previ- 
ous to  1830.  This  was  that  when  the  mortar  would  sustain  a  wire 


108        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


of  Vi2  inch  diameter  weighted  to  V4  pound,  it  should  be  said  to 
have  received  its  initial  set,  and  its  final  wheni  it  would  sustain  a 
wire  of  */2  inch  diameter  bearing  a  one-pound  weight.  The  actual 
setting-point  must  be  obtained  by  frequent  trials.  This  standard 
was  accepted  by  Gillmore  and  others,  and  is  the  one  in  general  use 
at  the  present  time. 

While  many  more  and  elaborate  tests  can  be  and  are  made  en 
cements,  those  for  fineness  and  tensile  strength  on  the  lines  herein 
indicated  will  give  good  and  safe  results  for  general  work. 

For  general  specifications,,  then,  it  would  seem  to  be  in  accord- 
ance with  best  practice  to  make  the  following  requirements  for 
fineness: 

PORTLAND    CEMENT. 

95%  to  pass  a  sieve  of     2,500  meshes  per  sq.  inch. 
85%    "      "  "  10,000        "        "      "      " 

70%    "      "  "  40,000        "         "      "       " 

NATURAL  CEMENT. 

92%  to  pass  a  sieve  Of     2,500  meshes  per  sq.  inch. 


85%    ' 
80%    " 


6,400 
10,000 


FOB   TENSILE    STRENGTH   PER    SQUARE   INCH. 


Portland  Cement. 

Natural  Cement. 

24  Hours. 

7  Days. 

28  Days. 

' 
24  Hours. 

7  Days. 

28  Days. 

Neat 
Ito2 
Ito3 

175 

400 
200 
125 

550 
300 
200 

50 

120 

50 

200 
120 

It  is  not  necessary,  however,  that  all  cements  should  reach  these 
figures.  But  it  should  be  provided  that  a  quick-setting  cement 
should  increase  a  certain  per  cent  over  its  24-hour  strength  in  30 
days,  and  that  a  slow-setting  cement  should  not  be  less  than  a 
specified  minimum  at  that  time,  and  particular  attention  should  be 
given  to  its  strength  with  the  sand  mixtures.. 

Just  what  requirements  should  be  called  for  in  special  cases  de- 


CEMENT,  CEMENT  MORTAR,  AND   CONCRETE.  109 

pend  upon  the  conditions  under  which  it  is  to  be  used.  It  can  be 
readily  understood  that  it  is  not  good  engineering  to  insist  upon,  a 
cement  conforming  to  certain  standards  in  all  cases  when  at  one 
time,  for  instance,  it  may  be  used  as  a  foundation  for  a  street  pave- 
ment in  dry  work,  and  at  another  be  laid  in  running  water.  In 
one  instance  a  quick-setting  cement  is  absolutely  necessary,  and 
in  the  other  one  that  is  moderately  slow  in  taking  its  initial  set 
is  better.  What  should  be  done  is  to  ascertain  what  the 
requirements  of  the  work  are  and  then  use  a  cement  that, 
as  it  is  generally  manufactured,  comes  the  nearest  to  meet- 
ing these  requirements.  Tests  should  be  continually  made  to 
ascertain  if  it  is  being  kept  up  to  its  standard.  One  principle 
should  be  strictly  adhered  to  in  making  tests  of  any  kind  of  ma- 
terial: have  the  conditions  governing  the  tests  conform  as  closely  as 
may  he  to  those  under  which  the  material  is  to  he  used.  Eliminate 
as  much  theory  and  uncertainty  as  possible,  and  spend  neither 
time  nor  money  in  attaining  a  requirement  that  will  never  be  of 
any  benefit  to  the  work. 

In  actual  construction  cement  is  almost  never  used  neat.  It  is 
first  mixed  with  sand  and  is  then  called  mortar.  The  common 
proportion  for  a  natural  cement  is  one  part  cement  to  two  parts  of 
sand  by  volume.  This  is,  of  course,  purely  arbitrary,  but  it  seems 
to  have  come  into  general  use  from  the  fact  that  this  mixture 
seems  to  be  strong  enough  for  the  more  common  uses  to  which 
cement  mortar  is  put.  When  a  greater  or  an  immediate  strength 
is  wanted  a  brand  of  Portland  is  adopted  with  varying  proportion 
of  sand.  Some  engineers  indeed  think  that  Portlands  run  more 
evenly  than  the  naturals,  and  that  where  only  a  moderate  strength 
is  required  the  latter  should  be  used,  reducing  the  expense  by  in- 
creasing the  proportion  of  sand. 

Ag  it  is  the  mortar  that  is  to  be  used,  whether  in  regular  masonry 
or  concrete,  it  is  important  and  necessary  to  know  the  resulting 
volume  from  the  mixing  of  cement  and  sand  in  different  propor- 
tions. 

It  should  be  specified',  also,  whether  the  cement  is  to  be  measured 
as  originally  packed  or  as  poured  loosely  into  the  measuring-box. 

Tables  Nos.  25  and  26  give  the  results  of  experiments  made  by 
L.  0.  Sabin,  U.  S.  Assistant  Engineer,  to  ascertain  the  amount  of 


110         STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


sand  and  cememt  required  to  make  a  cubic  yard  of  mortar  under 
different  conditions. 

TABLE  No.  25. 


B&rrds 

Barrels 
Cement. 

Barrels 
Cement. 

Cement. 
300  Ibs 

All  Sand 

Parts  of 
Sand  to 
one  of 
Cement. 

265  Ibs. 
71  Ibs.  per 
cu.  ft. 
Cement 
packed 
3.73  cu.  ft. 

Cubic  Yards 
Loose  Sand. 

280  Ibs. 
75  Ibs.  per 
cu.  ft. 
Cement 
packed 
3.73  cu.  ft. 

Cubic  Yards 
Loose  Sand. 

per  bbl'. 
80  Ibs.  per 
cu.  ft. 
Cement 
packed 
3.75  cu  ft. 

weighed 
100  Ibs.  per 
cu.  ft.,  voids 
37^}  percent. 
Cubic  Yards 
Loose  Sand. 

per  bbl. 

per  bbl. 

per  bbl. 

1 

4.45 

0.61 

4.32 

0.60 

4.17 

0.58 

2 

2.83 

0.78 

2.79 

0.77 

2.75 

0.76 

3 

2.04 

0.85 

2.03 

0.84 

2.00 

0.83 

4 

1.65 

0.89 

1.60 

0.88 

1.57 

0.87 

TABLE  No.  26. 

SAND   AND  CEMENT,    BOTH  LOOSE. 
Cement  weighs  60  Ibs.  per  cubic  foot. 


1 

2 
3 

4 

By  Volume,  Barrels  of  Cement. 

By  Weight,  Barrels  of  Cement. 

265  Ibs. 

280  Ibs. 

300  Ibs. 

Cu.  Yds. 
Sand. 

265  Ibs. 

280  Ibs. 

300  Ibs. 

Cu.  Yds. 
Sand. 

4.08 
2.49 
1.77 

3.86 
2.36 
1.68 

3.60 
2.20 
1.57 

0.67 
0.81 
0.87 

5.21 
3.66 
2.72 

2.15 

4.93 
3.46 
2.57 
2.03 

4.60 
3.23 
2.40 
1.90 

0.51 
0.72 
0.80 
0.84 

The  above,  while  being  very  valuable  as  showing  actual  amounts 
of  mortar  to  be  obtained  from  the  different  mixtures  of  cement 
and  sand,  also  emphasizes  the  importance  of  the  unit  to  be  used; 
as,  taking  the  barrel  of  cement  at  265  Ibs.  and  the  proportion  of 
one  part  cement  to  two  of  sand,  the  tables  give  the  following 
weights  of  cement  for  a  cubic  yard  of  mortar  by  each  of  the  dif- 
ferent methods: 

Pounds. 

By  volume,  cement  loose 660 

By  volume,  cement    packed 750 

By  weight 970 


CEMENT,  CEMENT  MORTAR,  AND   CONCRETE. 


in 


The  second  method  requires  13£  per  cent  and  the  third  almost 
50  per  cent  more  cement  than  the  first.  The  plain  and  true  infer- 
ence is  that  the  only  sure  way  of  knowing  just  how  much  cement  is 
being  used  is  to  determine  proportions  by  weight,  or  to  specify 
that  a  cubic  yard  of  mortar  shall  receive  so  many  pounds  of  cement. 
This  is  particularly  important  now  when  so  many  manufacturers 
deliver  their  cement  in  bags  by  weight,  and  allowing  a  certain  num- 
ber of  pounds  for  a  barrel.  When  heavier  cements,  as  the  Port- 
lands, are  used,  it  is  evident  that  there  will  not  be  so  much  differ- 
ence in  the  methods  employed. 

Cement  mortar  is  often  used  in  sea-water,  and  in  preparing 
it  considerable  extra  expense  would  be  incurred  in  providing  fresih 
water  for  the  mixture.  Quite  a  number  of  experiments  have  been 
made  at  various  times  and  by  different  persons  to  determine  the 
action  of  salt  water,  if  used  in  mixing,  and  also  when  the  mortar 
is  immersed  in  it. 

Gen.  Gillmore  made  some  rectangular  parallelepipeds  of  mortar 
2x2x8  inches  in  vertical  moulds  under  a  pressure  of  32  pounds  per 
square  inch  until  set.  These  were  broken  on  supports  from  a 
pressure  from  above  midway  between  the  supports.  The  specimens 
were  kept  in  a  damp  place  for  twenty-four  hours,  when  they  were 
placed  in  sea- water,  where  they  remained'  ninety-four  days,  till 
broken.  Table  No.  27  gives  his  results. 

TABLE  No.  27. 


Conditions. 

Breaking 
Strength 
in  Pounds. 

No. 

Broken. 

Neat  cement  mixed  with  fresh  water  

499* 

8 

«'         "          •«          "     sea-water  

3794 

8 

Cement  1    sand  2   by  volume  mixed  with  fresh  water 

3191 

5 

10.? 

Cement  1,  sand  2,  by  volume  mixed  with  sea-water,  concen- 
trated by  heat  25  per  cent  

195 
165 

2 

In  the  report  of  Mr.  E.  C.  Clarke  previously  referred  to  Table 
No.  28  is  given,  showing  the  results  of  his  investigations  on  this 
question. 


112        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


TABLE  No.  28. 

Figures  indicate  tensile  strength  per  square  inch. 


ROSENDALE. 

]  Cement,  1  Sand. 

PORTLAND. 
1  Cement,  2  Sand. 

Mixed  with     

Fresh 
Fresh 
40 
126 
247 
310 

Fresh 
Salt 
48 
135 
250 
253 

Salt 
Fresh 
50 
114 
243 
224 

Salt 
Salt 
61 
126 
224 
217 

Fresh 
Fresh 
151 
213 
314 
342 

Fresh 

Salt 
122 
191 
245 
231 

Salt 
Fresh 
152 
203 

277 
310 

Salt 
Salt 
149 
*00 
264 

Immersed  in  
1  week        

6  months  

Mr.  A.  S.  Cooper  in  a  paper  published  in  the  Journal  of  the 
Franklin  Institute,  October,  1899,  details  some  experiments  made 
by  him,  shown  in  Table  No.  29,  to  determine  the  effect  of  salt 
water.  The  briquettes  were  the  American  Society  of  Civil  Engi- 
neers' forms,  the  proportions  being  determined  by  weight.  They 
were  stored,  in  moist  air  for  twenty-four  hours  and  then  in  an 
immersion-tank  till  broken.  The  figures  represent  tensile  strength 
per  square  inch  in  pounds. 

TABLE  No.  29. 

PORTLAND  CEMENT.   STANDARD  SAND. 


1  Part  Cement, 
1  Part  Sand. 

1  Part  Cement, 
2  Parts  Sand. 

1  Part  Cement, 
3  Parts  Sand. 

Mixed  with... 
Immersed  in.  . 
7  days 

Fresh 
Fresh 
544 
574 
671 
833 
846 

Fresh 
Salt 
568 
709 
670 
708 
625 

Salt 
Fresh 
585 
621 
801 
820 
819 

Salt 
Salt 
618 
631 
660 
610 
318 

Fresh 
Fresh 

487 
560 
584 
627 
587 

Fresh 
Salt 
477 
586 
600 
637 
471 

Salt 
Fresh 
458 
507 
580 
630 
614 

Salt 
Salt 
492 

554 
583 
589 
478 

Fresh 
Fresh 

278 
335 
438 
444 
431 

Fresh 
Salt 
329 
376 
392 
397 
282 

Salt 
Fresh 
303 
880 
391 
408 
344 

Salt 
Salt 
270 
348 
400 
408 

3a*> 

28days  

3  months  
6  months  
1  year... 

NATURAL  CEMENT.   STANDARD  SAND. 


7  days  

266 

320 

237 

298 

147 

177 

134 

188 

65 

92 

87 

110 

28  days  

310 

331 

297 

384 

250 

256 

218 

243 

107 

150 

120 

164 

4  months  

385 

369 

400 

414 

296 

322 

335 

325 

223 

228 

230 

232 

6  months  

377 

388 

370 

368 

298 

325 

332 

334 

221 

223 

238 

237 

1  year  

305 

299 

356 

275 

235 

170 

207 

191 

200 

162 

173 

140 

While  the  actual  figures  given  by  Mr.  Clarke  and  Mr.  Cooper 
vary  much  as  to  the  actual  strength,  owing  doubtless  to  the  char- 
acter of  the  cement  and  the  method  of  manipulation,  they  are  rela- 
tively the  same,  there  being  a  marked  decline  whenever  the 
briquettes1  are  immersed  in  salt  water,  especially  the  long-time  tests 
with  the  Portland  cements.  Where  'the  mixing  is  done  with  salt 


CEMENT,   CEMENT  MORTAR,  AND   CONCRETE.  113 

water  and  the  immersing  in  fresh,  the  difference  is  not  so  striking. 
Although  these  tests  show  that  cement  mortar  is  weakened  by  the 
action  of  salt  water,  works  have  been  carried  on  of  sufficient  time 
and  extent  to  make  it  certain  that  the  deterioration  is  not  danger- 
ous. This  becomes  important  in  studying  the  action  of  frost  on 
mortars,  as  it  is  customary  to  add  salt  to  the  water  for  mortar-mix- 
ing, when  it  must  be  used  at  low  temperatures. 

Mr.  James  J.  11.  Croes  gives  as  a  rule:  "  Dissolve  1  pound  of  rock 
salt  in  18  gallons  of  water  when  the  temperature  is  at  32°  F.,  and 
add  3  ounces  for  every  3  degrees  of  temperature."  He  adds  that 
masonry  laid  with  such  mortar  stood  well  and  showed  no  signs  of 
having  been  affected  by  the  frost. 

Mr.  Alfred  Noblo  states  that  a  pier  was  built  on  the  Northern 
Pacific  Railroad  near  Duluth  at  a  temperature  varying  from  0  to 
20°.  Portland  cement  was  used  for  the  mortar  in  proportions  of 
1  to  1J  for  face  stone  and  1  to  2J  for  backing.  Salt  was  dissolved 
in  the  water,  and  the  sand  was  warmed.  The  mortar  froze  very 
quickly,  and  several  months  afterwards  was  found  to  have  perfectly 
set  and  to  be  in  as  good  condition  as  that  laid  in  milder  weather. 

Table  No.  30  gives  ihe  result  of  some  of  his  experiments  to 
determine  the  effect  of  salt  upon  the  mortar,  and  Table  No.  31  the 
combined  effect  of  salt  and  freezing. 

The  amount  of  salt  seems  to  make  no  material  difference,  al- 
though the  figures  are  slightly  less  for  the  greater  quantities,  and, 
as  in  the  previous  tables,  the  salt  water  gives  poorer  results  than 
the  fresh. 

These  figures  show  some  gain  when  salt  water  is  used  for  the 
mixture  and  the  briquettes  immersed  in  fresh,  and  decided  increase 
when  they  were  frozen  for  six  days  and  immersed  in  water  long 
enough  to  thaw,  but  not  a  sufficient  time  to  gain  an  additional  set. 
The  table  would  be  of  more  value  if  it  extended  over  a  longer 
period  of  time. 

Table  No.  32  is  taken  from  a  paper  read  before  the  Canadian 
Society  of  Civil  Engineers  in  February,  1895,  by  Prof.  Cecil  B. 
Smith  of  McGill  University. 

Set  No.  1  was  submerged,  after  24  -hours,  in  water  of  laboratory 
tank 


114        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


TABLE  No.  30. 

Proportions:  cement  1,  sand  1,  volume;  cement  21  ounces;  sand  23  ounces;  water  6  ounces. 
Figures  are  tensile  strength  per  square  inch. 


Salt. 

7  Days. 

30  Days. 

90  Days. 

6  Months. 

9  Months. 

12  Months 

18  Months 

2  Years. 

Ooz. 

155 

220 

289 

311 

390 

382 

402 

430 

* 

139 

200 

246 

288 

363 

364 

423 

346 

i 

139 

192 

221 

289 

352 

383 

392 

326 

128 

189 

217 

288 

343 

369 

350 

334 

TABLE  No.  31. 

PORTLAND   CEMENT. 
Mixture:  cement  35  oz.,  water  7  oz.,  salt  as  shown. 


Salt  in  Ounces. 

0 

^ 

y\ 

% 

\s 

429 
415 
394 
215 

% 

H 

415 
392 
390 
221 

% 

1 

Immersed  in  test-  room  when  removed  from 

327 
316 
336 
169 

357 
378 
422 
198 

375 
411 
421 
167 

392 
374 
399 

217 

402 
405 
384 
208 

388 
383 
356 
221 

402 
409 
387 
239 

Exposed  to  air  and  frozen  three  days,  then 
immersed  in  test-  room  four  days  

Immersed  in  test-room  when  removed  from 
moulds  

Exposed  to  air  and  frozen  six  days,  then 
exposed  to  air  in  test-room  at  70°  one  day. 

TABLE  No.  32. 


£2 

£2 

K 

3% 

3  3 

1 

Mixture. 

Age. 

No.  1. 

No.  2. 

No.  3. 

No.  4. 

a  on 

Is* 

?i^ 
pi 

,-• 

c 

Remarks. 

33  0*0 

!** 

d 

X 

Portland  neat 

2  Mos. 

602 

471 

282 

334 

-t-23°F. 

422°F. 

1(5 

1  to  1 

377 

276 

194 

233 

_l_  50 

4.310 

20 

2  to  1 

u 

168 

150 

105 

111 

-*• 

0° 

24 

3tol 

M 

104 

85 

92 

97 

-5° 

-  6° 

24 

3  and  4  showed  irregular 

and  injured  fractures. 

Natural  neat 

'« 

226 

221 

349 

0 

+  2° 

4-  5° 

•-24 

4    completely    blown    in 

fragments. 

1  tol 
Neat 

,t 

125 
250 

229 

281 

187 
159 

44 
94 

4-  8° 
4-13° 

+0.6° 

4-  5° 

22 
24 

Some  of  No.  4  injured. 
Mixed  with  water  at  122°F. 

1  to  1 

it 

129 

170 

80 

117 

4  9° 

0° 

20 

Mixed  with  water  at  118°F. 

Neat 

1  Month 

155 

278 

217 

249 

+17° 

+r*° 

•JO 

Mixed  with  2#  of  brine. 

CEMENT,   CEMENT  MORTAR,  AND   CONCRETE.  115 

Set  No.  2  was  kept  on  damp  boards  in  a  closed  tank  for  the 
whole  period,  and  never  allowed  to  dry  out. 

Set  No.  3  was  allowed  to  set  in  the  laboratory,  and  then  ex- 
posed to  the  severe  frost  and  left  in  open  air  for  the  whole  period. 

Set  No.  4  was  exposed  in  from  8  to  10  minutes  to  the  severe 
frost  and  left  there  for  the  whole  period. 

The  important  deductions  from  the  Portland  tests  are:  1.  That 
mortar  immersed  in  water  is  stronger  than  when  used  in  air;  2. 
That  mortar  exposed  to  temperature  below  freezing  and  kept  there 
till  set  is  stronger  than  when  allowed  to  set  in  air  and  then  ex- 
posed to  frost;  3.  That  mortar  kept  in  damp  air  was  the  weakest 
of  all  the  different  conditions  experimented  on. 

It  will  be  noticed  from  the  results  of  the  tests  of  the  natural 
cement:  1.  That,  contrary  to  the  Portlands,  these  cements  should 
not  be  used  if  the  mortar  must  be  exposed  at  once  to  frosts;  2~ 
That  from  the  neat  tests  no  time  deductions  can  be  made  of  a  sand 
mixture,  as  in  every  case  when  mixed  with  fresh  water  the  1-to-l 
compound  was  considerably  stronger  than  the  neat;  3.  That  No.  £ 
in  every  case  but  one  was  the  strongest,  while  with  the  Portland 
it  was  the  weakest;  4.  That  the  addition  of  salt  to  the  mixing 
water  added  very  materially  to  the  strength  of  the  briquettes  when 
exposed  to  the  frost. 

Table  No.  33  gives  the  results  of  some  experiments  made  by 
Mr.  A.  C.  Hobart  and  published  in  The  Technograph,  No.  12, 
1897-98. 

In  all  cases  the  briquettes  were  frozen  six  days  after  having 
been  allowed  to  set,  as  shown  in  the  table.  They  were  thawed 
from  18  to  20  hours  and  then  broken.  The  upper  line  of  figures 
for  each  mortar  is  the  strength  in  pounds  per  square  inch  of  the 
unfrozen  briquettes,  and  the  lower  is  the  percentage  of  the  strength 
frozen  to  the  strength  unfrozen. 

Table  No.  34  gives  the  result  of  some  tests  made  on  12-inch 
concrete  cubes  by  Mr.  W.  A.  Rogers,  Assistant  Engineer  of  the 
Chicago,  Milwaukee,  and  St.  Paul  Railway  at  Chicago.  "  Atlas  " 
Portland  and  Louisville  natural  cements  were  used.  The  propor- 
tions were:  Atlas,  1  cement,  3  gravel,  and  4  broken  stone;  and 
Louisville,  1  cement,  2  gravel,  and  4  broken  stone.  Eight  cubes 
were  made  of  each  cement,  two  being  mixed  with  water  to  which 


116        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

TABLE  No.  33. 


Portland. 


Age  in  Hours  when  Frozen. 


2tol 

Louisville  Star  neat. 

1  to  1 

2  to  1 

Akron  neat 

1  to  1  . 


Brand 

Dufassey  neat 

Ito  1 

2  to  1 

3  to  1 

Saylor's  American  neat. . . . 

1  to  1 

2  to  1 1 j 

3  to  1 | 

Natural. 
Clark's  Utica  neat \ 

1  to  1  . .  . .  \ 


2  to  1 

Louisville  Black  Diamond 
neat 

1  to  1  . , 


2tol 


321 
68 

133 
58 
33 
26 
00 
00 

285 
60 

144 
47 
61 
55 
18 
32 


120 

90 

114 

88 

45 

71 

145 

109 

136 

132 

96 

133 

108 

83 

71 

79 

57 

168 

116 

72 

108 

94 

63 

170 


337 
72 

177 
77 
43 
34 
00 
00 

238 
50 

176 
57 
81 
73 
26 
46 


116 

87 

118 

91 

60 

95 

135 

102 

139 

135 

104 

144 

112 

86 

69 

76 

70 

206 

173 

107 

152 

132 

76 

205 


3 

341 
73 
172 
75 
62 
48 
10 

8 

234 
50 
173 
56 
96 
86 
15 
27 


127 
95 

111 
86 
80 

127 

148 


372 
79 

172 
75 
58 
45 
14 
18 

268 
59 

175 
57 

102 
92 
33 
59 


152 

114 

128 

99 

83 

132 

156 


|  117 
130  164 
126  159 


106 
147 
109 

84 
143 
159 

83 


123 
171 
184 
142 
152 
167 
87 


244  256 

175  191 

109  119 

168  173 

148  150 

79  93 

213  251 


12 
374 

80 

184 

80 

79 

62 

19 

25 

284 

50 

179 

58 

129 

116 

48 

86 


163 
122 
131 
102 

74 
117 
151 
117 
141 
137 
106 
144 
156 
120 
160 
176 

85 
250 
223 
138 
220 
191 
101 
273 


24 

400 

80 

186 

79 

81 

63 

28 

37 

248 

45 

255 

79 

143 

129 

54 

96 


143 

107 

142 

110 

43 

68 

153 

115 

130 

126 

69 

96 

150 

114 

133 

148 

80 

235 

237 

138 

202 

176 

120 

316 


48 

352 

67 

187 
75 


60 
37 

47 
240 

56 
260 

79 
138 
120 

69 
113 


135 

79 

137 

105 

45 

71 

150 

93 

120 

114 

57 


142 
103 
131 
146 
80 
222 
228 
132 
185 
158 
104 
297 


379 

69 

193 

75 

103 

75 

48 

58 

300 

110 

271 

82 

146 

108 

74 

114 


140 
80 

107 
80 
49 
70 

133 
81 

108 
97 
64 


140 
105 
129 
137 

72 
189 
216 
126 
179 
12r 

78 
186 


168 
327 

52 
296 
105 
181 
100 
106 
103 
590 
110 
303 

68 
161 

98 

87 
121 


154 

70 

138 

100 

69 

83 

150 

81 

123 

100 

80 

107 

132 

93 

127 

130 

65 

108 

182 

104 

171 

91 

69 

157 


672 
100 
331 
102 
209 
114 
134 

93 
671 
105 
391 

87 
226 
128 
124 
125 


199 
89 

160 
81 
77 
91 

153 
79 

137 
92 
92 
93 

150 
97 

138 

115 
60 
82 

163 
93 

185 
93 
90 

120 


one  pint  of  salt  to  ten  quarts  of  water  had  been  added,  and  the 
others  with  fresh  water. 

Capacity  of  machine  185,000  pounds,  a  showed  signs  of  failure, 
I  showed  no  signs  of  failure.  The  cubes  kept  out  of  doors  were 
subjected  at  once  to  a  temperature  considerably  below  zero.  During 


CEMENT,  CEMENT  MORTAR,  AND   CONCRETE.  117 

TABLE  No.  34. 


Conditions  of  Cube  after  having  been 
Made. 

Asein 
Days. 

Kind  of 
Water. 

Atlas. 

Louis- 
ville. 

28 

Fresh 

a  185,000+ 

43,000 

Kept  out  of  doors                   

28 

115  000 

33  000 

Kept   out  of  doors   28    days   and   in 
office  28  days  

|   56 

« 

b  185,000-f 

52,500 

28 

Salt 

b  185,000+ 

35,000 

this  exposure  the  weather  was  the  coldest  experienced  in  Chicago 
for  twenty  years,  but  subsequently  grew  warmer,  so  the  cubes  froze 
during  the  night  and  thawed  during  the  day.  The  deductions  the 
author  of  the  paper  makes  for  the  mixture  is:  "Freezing  before 
setting  does  not  seem  to  injure  the  Portland-cement  concrete  even 
if,  after  having  frozen  hard,  the  concrete  is  exposed  to  freezing 
and  thawing  weather.  Exposing  green  Portland  cement  concrete  to 
a  freezing  temperature  seems  to  affect  its  rate  of  hardening,  making 
it  slower,  but  eventually  the  concrete  will  be  just  as  good  as  if  it  had 
not  been  exposed  to  the  cold.  The  use  of  salt  seems  largely  to 
counteract  the  effect  of  cold  in  causing  slow  hardening."  He  also 
makes  the  same  deductions  for  Louisville  cement,  except  that  he 
thinks  the  use  of  salt  seems  to  have  little  if  any  effect  on  the 
strength  of  the  cubes  exposed  to  the  cold. 

Mr.  Noble  describes  the  construction  of  an  anchor-block  of  con- 
crete. This  was  built  during  freezing  weather,  a  portion  of  the 
time  below  zero,  with  about  one-half  of  the  mass  below  water. 
The  mixture  was  1  part  Milwaukee  cement,  2  parts  sand,  and  4  to 
5  parts  broken  stone.  The  material  and  water  were  heated,  a  double 
handful  of  salt  being  added  to  each  part  of  water.  Ice  formed 
over  the  top  of  the  concrete  every  night  until  the  mass  was  above 
the  water-level.  No  attempt  was  made  to  protect  the  concrete  from 
frost,  and  six  months  after  it  was  laid  it  was  found  to  be  thor- 
oughly set. 

These  experiments  cover  quite  a  period  of  time  and  were  made 
by  different  people  under  very  different  conditions.  As  a  rule 
the  same  general  deductions  can  be  made  from  them.  That  is, 
that  with  proper  precautions  good  results  can  be  obtained  by  the 
use  of  cement  mortar  in  cold  weather;  that  a  freezing  temperature 


118        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

greatly  retards  the  setting  of  mortar,  but  does  not  seriously  injure 
it  if  properly  treated;  that  it  is  much  safer  to  use  Portland 
cement  in  cold  weather,  especially  if  the  mortar  is  to  be  subjected 
to  alternate  freezing  and  thawing.  The  one  exception  to  the  lat- 
ter conclusion  is  the  experiments  of  Mr.  Hobart.  His  results  would 
show  that  the  American  cements  are  not  only  influenced  less  by 
freezing  than  the  Portlands,  but  that  their  strength  is  actually  in- 
creased. Mr.  Hobart  says  that  this  is  so  different  from  all  the 
former  ideas  on  the  subject  that  some  of  the  tests,  were  carefully 
duplicated  with  practically  the  same  results. 

Specifications  for  work  involving  the  use  of  cement  mortar  al- 
ways provide  that  it  shall  be  used  within  a  certain  time  after  it 
has  been  mixed,  generally  from  half  an  hour  to  an  hour  and  a  half, 
according  to  the  character  of  the  work  and  the  nature  of  the  par- 
ticular cement.  This  is  because  it  is  considered  that  cement  mortar 
should  be  in  its  permanent  place  before  it  has  begun  to  set,  and 
that  any  disturbance  after  the  first  set  reduces  its  ultimate  strength. 
Not  many  experiments  have  been  made  to  demonstrate  this,  and 
it  can  be  readily  understood  that  to  be  of  value  tests  must  be 
made  of  each  individual  cement.  A  slow-setting  cement  will  of 
course  permit  more  manipulation  and  disturbance  than  one  that 
sets  qnicklj,  and  just  what  the  effect  will  be  can  only  be  known 
by  experiment.  Table  No.  35  shows  the  result  of  some  experiments 
detailed  by  Gen.  Gillmore.  The  sections  used  and  the  methods 
of  constructing  and  breaking  were  the  same  as  on  page  111,  except 
that  the  mortar  was  made  of  equal  parts  of  natural  cement  and 
sand  by  volume,  and  the  samples  were  kept  in  sea-water  for  320 
days. 

TABLE  No.  35. 

Breaking  Strength. 

Cement  fresh  from  barrel,  average  of  five ...     767  Ibs. 

"        repulverized  after  3  days'  set,  average  of  six 236|  " 

ANOTHER   BRAND. 

Cement  fresh  from  barrel,  average  of  four. 631  Ibs. 

"        repulverized  after  3  days'  set,  average  of  ten 261    " 

Table  No.  36  gives  the  results  of  Mr.  Cooper  as  published  in 
the  paper  previously  referred  to.  The  briquettes  were  made  of 
Portland-cement  mortar  mixed  1 :  2  and  broken  at  the  end  of  one 


CEMENT,   CEMENT  MORTAR,  AND   CONCRETE. 


119 


year.  The  figures  represent  tensile  strength  in  pounds  per  square 
inch,  and  the  different  columns  show  the  time  of  making  the 
briquettes  after  the  mixing  of  the  mortar. 

TABLE  No.  3G. 


Kind  of  Sand. 

Per 
Cent  of 
Water. 

Made 
when 
Mixed. 

Number  of  Hours  Made  after  Mixing. 

1 

2 

3 

4 

5 

6    j     7 

8^ 

Beach  

14 

9.7 
15.3 
13.9 

232 
182 
240 
244 

248 
181 
230 
233 

227 
172 
245 
194 

211 
176 
227 

,, 

24( 

0-)( 

258 

226 
23; 

236 

liiver                                  . 

The  author  of  the  paper  concludes:  "  In  practical  working  with 
most  Portland  cement,  if  it  becomes  necessary  for  the  mortar  to 
stand  for  one-half  of  a  day  even,  no  injury  will  result,  provided 
the  precaution  is  taken  to  keep  the  mortar  wet." 

Another  test  to  which  cements  are  generally  put  is  the  one  for 
maintaining  its  volume.  This  is  sometimes  done  by  placing  the 
mortar  in  a  cylinder  of  glass.  If  any  expansion  takes  place  in 
setting,  the  glass  will  be  broken,  and  if  any  shrinkage,  it  can  be 
easily  detected.  Mr.  Clarke  says  in  the  Boston  Main  Drainage 
Report  that  in  his  tests  the  cylinders  were  invariably  broken.  An- 
other method  is  the  so-called  "  hot  water  "  test.  The  Faija  method 
is  to  mix  a  small  pat  of  cement  with  as  little  water  as  possible,  and 
place  it  on  a  glass  plate  in  a  covered  vessel  which  contains  water 
maintained  at  a  temperature  of  about  112°.  The  pat  is  kept  in. 
the  moist  air  for  6  or  8  hours,  when  it  is  immersed  in  water 
kept  at  a  temperature  of  from  115°  to  120°  Fahrenheit  for  the 
remainder  of  24  hours.  If  at  the  end  of  that  time  it  remains  intact 
with  no  signs  of  disintegration,  it  is  ready  for  use.  Manufacturers, 
however,  can  overcome  the  effect  of  the  heat  by  adding  sulphate  of 
lime  to  the  cement.  In  speaking  of  hot-water  tests,  Mr.  Cummings 
in  his  work  heretofore  referred  to  says:  "  It  is  safe  to  assert  that 
of  the  more  than  one  hundred  and  fifty  million  barrels  of  American 
rock  cements  used  in  all  of  the  great  engineering  works  through- 
out the  country  during  the  past  fifty  years,  and  with  no  evidence 
of  failure,  not  one  per  cent  would  have  sustained  the  boiline;  test. 
A  cement,  whether  natural  or  artificial,  that  will  crystallize  so 
rapidly  as  to  sustain  the  boiling  test  ought  to  be  looked  upon  with 


120        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

suspicion,  as  it  is  either  naturally  too  quick-setting  or  too  fresh  and 
lacking  in  proper  seasoning." 

Concrete. 

Concrete  can  be  defined  as  masonry  made  up  of  broken  stone, 
gravel,  cinders,  or  other  similar  material,  joined  together  by  cement 
mortar.  It  has  been  in  use  for  centuries.  One  of  the  oldest  and 
most  noted  examples  of  concrete  construction  is  that  of  the  dome 
of  the  Pantheon  at  Rome.  In  early  times  it  was  used  principally 
for  foundations.  But  as  its  value  has  become  recognized  and  cement 
has  been  produced  better  and  more  cheaply,  its  use  has  been  ex- 
tended until  now  it  is  put  to  practically  as  many  uses  as  is  stone 
itself.  It  is  used  as  a  monolith  and  also  in  blocks.  It  is  particu- 
larly adapted  to  foundations  of  irregular  form,  as  it  is  cheaply  and 
easily  shaped.  It  is  used  extensively  in  foundations  for  all  classes 
of  work,  bridge  piers  and  abutments,  sidewalks,  curbing,  sewer-pipe, 
fire-proof  floors,  and  even  as  a  monolith  in  arch  bridges  of  quite  ex- 
tensive spans.  Stone  suitable  for  concrete  is  often  found  in  locali- 
ties where  good  building-stone  is  not  obtainable,  and  thus  the  use 
of  concrete  allows  masonry  construction  when  the  cost  of  natural 
stone  would  have  been  prohibitive.  So  it  is  not  strange  that  it  has 
become  popular  with  engineers,  as,  when  well  made,  its  success  has 
always  been  as  great  as  its  adaptability. 

One  of  the  best  examples  of  concrete  construction  of  modern 
times  is  the  Museum  building  of  the  Leland  Stanford  Jr.  University 
of  California.  The  entire  building  is  practically  a  monolith. 

In  specifying  proportions  for  concrete-mixing,  it  is  customary 
to  regulate  them  in  units  of  cement.  This  is  not  the  true  way, 
and  there  is  a  growing  tendency  among  engineers  to  change  this 
and  establish  instead  a  certain  quantity  of  mortar  as  standard  unit. 
The  province  of  the  mortar  is  to  bind  the  pieces  of  stone  together, 
and  when  the  voids  of  stone  are  positively  filled,  any  excess  is  simply 
wasted.  In  deciding,  then,  upon  the  proportions  to  be  used  in  the 
concrete,  the  amount  of  voids  in  the  stone  adopted  must  be  first 
ascertained.  This  will  vary  with  different  kinds  of  stone  and  ac- 
cording to  the  uniformity  with  which  it  is  broken.  The  actual  size 
of  the  stone  does  not  make  so  much  difference.  When  the  pieces  are 
approximately  cubical  and  of  about  the  same  size,  the  voids  will 
"be  about  50  per  cent  of  the  stone.  By  grading  the  sizes,  however, 


CEMENT,   CEMENT  MORTAR,  AND   CONCRETE.  121 

from  the  largest  to  a  permissible  minimum,  the  amount  of  voids 
can  be  materially  reduced,  thus  accomplishing  a  saving  of  mortar 
and  increasing  the  strength  of  the  mixture.  In  order  to  insure  the 
complete  filling  of  the  voids  and  making  as  solid  a  mass  as  possible, 
it  is  best  to  specify  an  amount  of  mortar,  about  ten  per  cent  in  excess 
of  actual  voids,  as  perfect  work  is  very  seldom  attainable  in  prac- 
tice. 

The  exact  composition  of  the  mortar  is  important.  The  char- 
acter of  the  work  must  determine  the  strength  required  for  the 
concrete.  Kecognizing,  then,  that  a  concrete  cannot  be  stronger 
than  its  mortar,  the  proportions  of  the  concrete  and  sand  can  be 
decided  upon.  For  a  good  concrete,  stone  should  be  hard,  tough, 
and  of  such  a  texture  as  to  permit  of  strong  cohesion  between  the 
mortar  and  the  different  fragments.  But  it  would  not  be  allowable, 
or  good  engineering,  to  go  to  great  expense  to  provide  a  stone  that 
would  be  appreciably  stronger  than  the  mortar  matrix.  The  ideal 
concrete  would  have  its  stone  and  mortar  of  equal  strength,  so 
that  when  broken  the  fracture  will  extend  through  mortar  and 
stone  alike.  Clean  gravel  and  gravel  mixed  with  broken  stone  have 
been  used  with  great  success.  In  concrete  for  fire-proof  floors, 
where  weight  is  an  important  consideration,  clean  steam  cinders  are 
generally  employed.  This  gives  good  results,  and  some  of  the  tests 
of  very  flat  arches  made  of  this  material  show  that  its  strength  is 
surprisingly  great. 

After  having  determined  upon  the  amount  and  composition  of 
the  mortar  required  for  any  given  amount  of  stone,  the  next  step 
is  its  preparation.  The  sand  and  cement  should  first  be  thoroughly 
mixed  dry.  The  importance  of  this  cannot  be  overestimated. 
Without  good  mortar  good  concrete  cannot  be  obtained.  It  is  not 
sufficient  that  enough  and  good  materials  are  provided,  but  they 
roust  also  be  properly  applied.  Water  should  next  be  added  in 
such  quantity  as  will  assure  the  desired  consistency,  without 
drowning  out  the  cement,  and  the  entire  mass  mixed  rapidly  until 
every  grain  of  sand  is  coated  with  cement,  as  this  acts  with  the 
sand  in  precisely  the  same  manner  as  the  mortar  acts  with  the 
stone.  It  is  miniature  concrete.  As  it  is  desirable  to  have  as  great 
cohesion  as  possible  between  the  mortar  and  the  stone,  the  latter 
should  be  thoroughly  wet,  so  as  to  wash  off  all  dust  or  other  foreign 
matter,  and  then  added  to  the  mortar. 


122        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

The  resulting  mass  must  then  be  turned  over  forward  and  back- 
ward until  the  mortar  is  scattered  evenly  among  the  interstices  of 
the  stone,  so  that  each  piece  is  completely  covered  and  the  con- 
crete is  finished.  The  material  at  all  times  must  be  kept  on  boards 
or  platforms,  so  that  it  shall  be  kept  free  from  all  foreign  matter. 
This  operation  of  mixing  should  be  done  without  delay  and  as 
cxpeditiously  as  possible,  as  the  sooner  the  concrete  is  in  place  the 
more  complete  will  be  its  final  set.  The  place  of  mixing  should  be 
near  its  final  location,  preferably  so  that  it  can  be  shovelled  to  it 
from  the  boards;  but  this  is  seldom  possible,  and  it  must  be 
carried  in  some  conveyance  and  dumped.  When  used  in  any  great 
mass  it  should  be  spread  in  layers  from  9  to  12  inches  in  depth 
and  at  once  thoroughly  tamped  till  the  mortar  flushes  to  the 
surface,  and'then  left  undisturbed  till  completely  set,  or  till  another 
layer  is  ready  to  be  placed  upon  it.  In  such  work  it  is  better  to  have 
one  layer  follow  another  before  the  first  -has  entirely  set,  so  that 
they  can  become  thoroughly  bonded  together.  Whenever  fresh 
material  is  placed  upon  or  against  old  that  has  become  dry  and 
l.ard,  .the  latter  should  first  be  wet  in  order  to  aid  in  this  bonding. 

The  amount  of  materials  of  the  different  kinds  necessary  to 
produce  a  given  quantity  of  concrete  is  important.  Enough  has 
already  been  said  to  show  upon  what  this  is  conditioned.  Whether 
it  will  be  economy  to  mix  gravel  with  the  broken  stone  if  that  b£ 
used,  or  whether  one  or  the  other  is  to  be  adopted,  depends  upon 
the  ease  with  which  they  can  be  obtained  and  their  relative  values. 
It  is  the  business  of  the  engineer  to  study  this  question  till  it 
can  be  correctly  settled.  Having  then  'determined  upon  the  aggre- 
gate, and  the  amount  of  voids  it  contains,  the  amount  of  mortar 
is  at  once  decided  upon.  Ordinary  sand  contains  loose  about 
37£  per  cent  of  voids.  Some  tests  to  determine  this,  made  in  the 
laboratory  of  the  Department  of  Highways,  Borough  of  Brooklyn, 
New  York  City,  resulted  as  follows: 

Per  cent. 

Street  sand:    sample  No.  1,  compact,  voids 28.3 

sample  No.  1,  loose,  voids 37.6 

sample  No.  2,     "         "    35.0 

sample  No.  3,      "         "     37.5 

Standard  sand :    compact,  voids 44 

loose,  "    52.75 


CEMENT,   CEMENT  MORTAR,  AND   CONCRETE.  123 

Mortar  mixed  with  No.  3  in  the  proportion  of  1  cement  to  2 
sand  and  tamped  into  a  mould  till  the  water  flushed  to  the  surface 
gave  a  resulting  volume  of  2.07  parts,  showing  but  little  increase 
over  the  original  bulk  of  sand.  A  similar  mortar  mixed  with  four 
volumes  of  1-inch  broken  stone,  very  uniform  in  size,  in  which  the 
voids  had  been  found  to  be  51  per  cent,  thoroughly  tamped  as  be- 
fore, produced  a  volume  of  4.04  parts  of  concrete,  although*  it  was 
discernible  to  the  eye  that  all  the  voids  had  not  been  filled. 

In  Paper  No.  855  of  the  American  Society  of  Civil  Engineers 
will  be  found  much  information  on  concrete.  Mr.  Geo.  W.  Rafter 
made  many  experiments  to  determine  the  actual  amount  of  mortar 
and  concrete  obtained  with  different  proportions  of  sand,  cement, 
and  broken  stone.  The  experiments  were  made  with  dry,  plastic, 
and  excess  mortars.  The  results  are  given  in  Table  No.  37  for 
plastic,  as  that  is  the  consistency  which  would  be  the  most  liable 
to  be  used  in  actual  work.  Slightly  different  amounts  were  ob- 
tained with  different  brands  of  cements,  and  the  mean  is  given. 


TABLE  No.  37. 


Parts 
Cement. 

Parts  Sand. 

Mortar. 

Stone. 

Concrete. 

Mortar 
Percentage 
of  Stone. 

Shrinkage 
of  Stone, 
per  cent. 

1 

1 

1.83 

5.51 

5.01 

33 

9.1 

1 

1 

1.66 

4.14 

3.82 

40 

7.7 

1 

2 

2.45 

7.28 

6.62 

33 

9.1 

1 

2 

2.50 

6.28 

5.83 

40 

7.1 

1 

3 

3.30 

9.92 

8.89 

33 

10.4 

1 

3 

3.31 

8.23 

7.62 

40 

7.3 

1 

4 

4.28 

12.94 

11.66 

33 

9.9 

1 

4 

4.35 

10.96 

10.09 

40 

8.0 

1 

5 

5.04 

15.05 

14.29 

33 

8.3 

From  these  amounts  of  mortar  it  would  seem  that  the  sand  used 
must  have  been  very  compact,  containing  very  few  voids,  as  the 
1-to-l  mixture  increased  83  per  cent  over  the  volume  of  sand,  while 
the  l-to-5  even  had  a  slight  increase  in  volume.  The  resulting 
volumes  of  concrete,  on  the  other  hand,  indicate  a  large  amount  of 
voids  in  the  stone,  as  in  every  case  there  was  a  material  decrease  in 
the  original  volume  of  stone  used. 


124        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


In  a  discussion  on  the  above  paper,  Mr.  Wm.  M.  Hall  gives  the 
voids  found  by  him  in  sand,  gravel,  broken  stone,  and  the  two  last 
combined  in  different  proportions. 

TABLE  No.  38. 

SAND   31   PER  CENT.,    ITS   SIZE  BEING  AS  FOLLOWS  : 

'  Per  cent,  by  Volume. 

Held  by  a  No.  20  sieve  ............................     11 

Passed  by  a  No.  20  and  held  by  No.  30  .............     14 

"      "        "     30   "       "     "     "     50  .............     53 


50 


22 


CRUSHED   STONE   AND  GRAVEL  AND  MIXTURES   OF  THE  TWO. 

Voids. 

100$  of  crushed  2^-in.  stone 48# 

80     "    2£  "   "   20  of  lt-in.  gravel  44 

70     "    2£  "   "   30  "  1^  "    "   41 

60     "    2i  "   "   40"  H  "    "   38^ 

50     "    2i  "   "   50  "  1£  "    "   36 

100  "  H  "    "   35 

TABLE  No.  39. 


Sand. 

Sand- 
stone. 

Boulder 
Stone. 

Gravel. 

Furnace 
Slag. 

Per  cent. 

Per  cent. 
100 

Per  cent. 
100 

Per  cent. 
100 

Per  cent. 

Retained  on  1-inch,  finer 

100 

100 

10.70 

23.65 

1   10 

8  70 

2.86 

««            10     "    

17.14 

45.62 

20     "    
30     "    
"           40     "    

4.17 
12.52 
44.44 

38.87 





21.76 
6.49 
5.96 
5.99 

36.92 
8.26 
3.24 
2.00 

Voids  

41.7 

45.3 

48.7 

34.08 

43.8 

The  dust  had  been  screened  out  of  the  stone,  and  the  sand  from 
the  gravel.  The  slight  'difference  in  voids  between  the  last  mix- 
ture ajid  the  gravel  alone  would  indicate  that  the  limit  of  the  reduc- 
tion in  voids  had  been  practically  reached. 

Mr.  H.  Von  Schon,  in  further  discussing  this  same  paper,  gives 
among  others  a  table  showing  voids  found  in  different  materials, 
and  how  they  were  graded  as  to  size.  This  is  reproduced  as  Table 
No.  39. 


CEMENT,   CEMENT  MORTAR,  AND   CONCRETE.  125 

So  much  attention  has  been  given  to  voids,  as  it  is  absolutely 
necessary  to  know  the  space  to  be  filled  by  the  mortar  in  order  to 
get  the  best  concrete,  as  well  as  to  tell  how  much  will  be  obtained 
from  a  given  mixture.  The  amount  of  tamping  it  receives  will 
also  affect  the  quantity  materially  up  to  the  point  of  filling  the 
voids. 

The  proper  consistency  for  a  concrete  mixture  is  a  question  that 
has  been  much  discussed  by  engineers.  As  it  requires  much  less 
labor  to  mix  it  when  an  excess  of  water  is  used,  contractors  and 
laborers  always  have  a  tendency  to  add  as  much  as  permitted,  and 
constant  restraint  is  required  to  restrict  them.  The  general  theory 
is  that  a  medium  dry  concrete  will  be  stronger  than  one  mixed  with 
more  water.  This  is  probably  true  theoretically,  and  would  most 
likely  be  borne  out  in  tests;  but  it  must  *be  remembered  that  such 
a  mixture  would  require  much  more  tamping  to  become  thoroughly 
compacted  than  one  more  plastic,  and  also  that  extreme  vigilance  is 
necessary  in  order  to  obtain  it;  also  that  the  mixing  itself  will  not 
be  so  evenly  done  if  dry.  Then,  too,  if  the  concrete  is  spread  out 
in  thin  layers,  as  is  done  in  the  case  of  foundations  for  street  pave- 
ments, a  portion  of  the  water  will  be  evaporated  before  it  has  had 
a  chance  to  combine  with  the  cement,  and  the  mortar  will  simply 
dry  out  rather  than  set.  This  is  particularly  the  case  in  hot 
weather;  and  although  the  tendency  can  be  somewhat  overcome  by 
keeping  the  concrete  wet  by  sprinkling,  the  results  will  not  be  as 
good.  The  author  was  brought  up  in  the  dry  school,  but  his  own 
experience  has  taught  him  that  it  is  safer  to  have  the  mixture  a 
little  wet  rather  than  a  little  dry.  The  immediate  result  is  to 
retard  the  setting,  but  as  time  passes  its  strength  increases,  and  it 
is  very  doubtful  if  it  be  appreciably  weaker  at  the  end  of  a  few 
months.  The  ratios  for  strength  of  the  different  concretes  made 
by  Mr.  Eafter  were:  dry  mortar  29.1,  plastic  26.6,  and  excess  25.3, 
taking  the  average  of  ten  tests. 

Concrete  is  often  mixed  by  machinery,  and  much  discussion 
has  arisen  over  the  value  of  this  method  as  compared  to  hand 
mixing.  Much  can  be  said  on  both  sides.  Many  machines  have 
been  devised  for  this  purpose,  and  varying  results  will  be  arrived 
at  with  each.  In  hand  mixing  the  cement  and  sand  should  be  first 
measured  out  in  the  proper  proportions  and  then  carefully  mixed 


126        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

dry  on  a  smooth  platform.  Enough  water  should  then  be  added 
to  make  a  mortar  of  the  desired  consistency,  when  the  whole  mass 
should  again  be  mixed.  The  first  requisite  is  to  have  a  good 
mortar.  Whatever  the  aggregate  to  be  used,  it  should  be  free  from 
all  dust  or  sand  and  thoroughly  drenched,  so  that  it  shall  be  clean 
and  damp  in  order  that  the  mortar  will  readily  cling  to  it.  The 
mortar  should  then  be  spread  upon  the  board  and  the  stone  added. 
Workmen  should  then  proceed  with  the  mixing,  working  from  the 
bottom  and  throwing  all  material  from  the  centre  to  the  sides, 
turning  their  shovels  downward  in  so  doing.  It  should  then  be  all 
thrown  back  in  the  same  manner,  forming  a  pile  in  the  centre.  If 
this  be  carefully  done,  the  stones  are  generally  all  coated  and  the 
concrete  should  then  be  placed  in  its  permanent  position.  If  the 
work  is  well  carried  out,  .there  will  be  no  question  but  that  good 
results  will  be  obtained. 

There  are  several  kinds  of  machine  mixers.  One  is  formed 
of  a  cubical  iron  box  of  any  desired  size,  with  trunnions  fastened 
at  opposite  diagonal  corners,  and  supported  by  uprights.  One  side 
of  the  box  can  be  easily  taken  off  for  loading  and  unloading.  A 
charge  of  cement,  sand,  stone,  and  water  is  measured  and  placed 
in  the  box.  The  loose  side  is  then  bolted  on  and  the  box  revolved 
by  any  convenient  power  until  the  ingredients  are  thoroughly 
mixed. 

Another  which  has  been  used  much  in  Brooklyn  on  street  work 
is  a  portable  machine  s'hown  in  Fig.  2.  The  boiler  and  mixer  are 
mounted  on  four  low  wheels  and  can  be  moved  by  a  pair  of  horses 
as  the  work  progresses,  or  by  the  men  on  the  street.  It  consists  of 
a  square  shaft  running  lengthwise  of  a  horizontal  semi-cylinder 
about  28  inches  in  diameter  and  8  feet  long.  The  cylinder  is  firmly 
set  in  a  frame.  To  the  shaft  are  attached  cast-iron  blades  of  such 
length  as  will  give  a  little  space  between  the  ends  and  the  cylinder, 
and  at  an  angle  inclined  to  the  shaft  so  that  as  it  is  revolved  the 
material  moves  towards  the  end.  If  it  move  too  freely,  so  that  it 
reaches  the  end  before  it  is  thoroughly  mixed,  a  few  of  the  blades 
near  the  centre  can  be  reversed,  thus  checking  the  forward  motion. 
Wrater  is  supplied  by  a  perforated  iron  pipe  running  along  one 
side  and  connected  by  hose  to  a  hydrant,  the  amount  being  regu- 
lated by  a  stop-cock.  A  little  room  is  left  near  the  end  to  allow 


FIG    i.'. 


127 


CEMENT,  CEMENT  MORTAR,  AND   CONCRETE.  129 

about  a  wheelbarrowful  of  concrete  to  accumulate,  when  the  end 
gate  is  raised  and  the  concrete  dumped  into  the  waiting  barrow 
and  then  wheeled  to  any  desired  location.  At  the  other  end  of  the 
machine  the  boiler  and  engine  are  located.  When  the  machine  is 
operated  continuously  the  boiler  requires  about  one-half  ton  of 
coal  per  day,  the  same  man  acting  as  engineer  and  fireman. 

To  operate  it  to  advantage,  the  machine  is  located  in  the  centre 
of  the  roadway  and  the  broken  stone  dumped  upon  planks  upon 
one  side  and  the  sand  and  cement  on  the  other.  The  latter  are 
carefully  measured  out  and  mixed  dry  in  a  long  pile  on  a  con- 
tinuous platform.  Men  with  shovels  are  stationed  on  each  side, 
the  number  corresponding  to  the  proportion  of  mortar  and  stone 
desired,  and  throw  the  material  towards  the  back  end  of  the  shaft 
so  that  it  may  have  the  benefit  of  all  the  blades  in  the  mixing.  As 
the  shaft  revolves  the  mass  moves  forward  according  to  the  speed 
of  the  engine  and  the  pitch  of  the  blades.  As  the  concrete  falls 
into  the  wheelbarrow  an  experienced  foreman  or  inspector  can 
readily  detect  if  it  be  not  properly  mixed  and  apply  the  remedy,  so 
that  in  a  very  short  time  the  machine  will  be  operating  success- 
fully. No  attempt  is  made  to  measure  the  stone,  as  it  can  be  told 
by  inspection  whether  sufficient  mortar  is  present  to  fill  thoroughly 
the  voids,  and  that  is  all  that  is  necessary.  If  too  much  or  too  lit- 
tle mortar  is  being  used,  the  trouble  is  remedied  by  adding  to  or 
taking  from  the  men  at  work  on  the  stone  as  the  occasion  requires. 
This  machine  has  a  capacity  of  about  150  cubic  yards  of  concrete 
per  day  when  running  smoothly  under  a  capable  foreman. 

Another  machine  is  called  "  The  Portable  Gravity  Concrete 
Mixer  "  and  consists  of  a  short  steel  trough  filled  with  numerous 
rows  of  steel  pins,  staggered  to  mix  thoroughly  the  sand,  cement, 
and  broken  stone  that  are  to  compose  the  concrete  as  they  gravitate 
through  the  trough.  At  the  upper  ends  of  the  trough  the  pins  in 
the  first  row  are  spaced  nearer  together  than  the  pins  in  the  other 
row,  in  order  that  the  stone  passing  the  first  row  will  go  through 
the  rest  of  the  mixer  without  clogging. 

The  water  is  led  from  a  barrel  by  a  l|-inch  hose  to  the  spray- 
pipe.  The  man  at  the  bottom  of  the  mixer  who  can  best  see  the 
concrete  operates  the  water-valve.  The  water  from  the  spray-pipe 
strikes  the  mixer  at  about  midway  its  length.  By  this  arrange- 


130        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

ment  the  concrete  is  mixed  dry  in  the  upper  half  and  wet  in  the 
lower  half. 

It  is  claimed  for  this  mixer  that  concrete  in  rolling  over  and 
over  on  the  bottom  of  a  steel  trough  ten  feet  long,,  each  and  every 
stone  being  thrown  from  side  to  side  by  each  row  of  pins,  is  mixed 
better  than  it  is  possible  to  mix  it  by  hand  or  steam. 

The  trough  delivers  the  concrete  in  a  wheelbarrow  or  other 
receptacle,  when  it  can  be  removed  as  desired. 

It  is  probable  that  good  results  will  be  obtained  by  using  either 
of  these  machines;  and  which  would  be  the  best  for  any  particular 
work  would  have  to  be  decided  by  the  conditions. 

The  first  or  box  machine  would  not  be  adapted  to  street  work, 
as  it  is  not  easily  moved  and  its  action  is  not  continuous.  Wherever 
it  is  desired  to  have  a  special  amount  mixed,  as,  for  instance,  in 
making  a  cement  sewer-pipe,  this  plan  will  insure  the  proper 
amount  with  very  little  waste,  as  all  ingredients  can  be  measured 
before  being  mixed. 

By  the  last  method  it  will  be  noticed  that  all  material  must  be 
raised  several  feet  above  the  place  of  delivery.  This  would  be  well 
adapted  for  concrete  to  be  used  in  basements,  as  the  material  would 
all  be  naturally  delivered  at  the  street-level  and  must  in  any  event 
be  lowered  to  where  it  was  to  be  used;  or  for  work  in  trenches,  or 
in  fact  under  any  conditions  where  the  concrete  would  be  needed 
several  feet  below  the  natural  delivery  of  the  material. 

By  either  of  these  two  machines  the  proportions  of  the  different 
ingredients  would  probably  be  more  accurately  determined  than  by 
the  second  one  described.  But  that  has  the  advantage  of  being 
easily  and  quickly  moved  (a  great  desideratum  in  street  work,  espe- 
cially in  a  narrow  roadway)  and  is  in  a  good  position  to  be  changed 
easily.  Its  results  are  certainly  satisfactory  when  under  the 
charge  of  intelligent  workmen;  but  if  operated  by  careless  and 
unskilled  laborers,  the  material  would  probably  not  be  as  well  mixed 
as  by  either  of  the  other  machines.  In  other  words,  it  requires  more 
intelligent  supervision. 

As  to  the  question  whether  concrete  mixed  by  hand  is  better 
than  that  mixed  by  machine,  it  can  be  said  that  the  product  of 
either  is  good  when  properly  made,  and  that  incompetent  workmen 
will  spoil  both.  Mixing  mortar  and  stone  is  hard  work,  and  labor- 


CEMENT,   CEMENT  MORTAR,  AND   CONCRETE.  131 

ers  will  shirk  it  whenever  possible;  so  that  if  proper  systems  are 
adopted  for  obtaining  and  applying  the  right  proportions,  it  would 
seem  that  concrete  mixed  by  machinery  ought  to  give  more  uniform 
results  than  that  mixed  by  hand. 

In  the  preceding  pages  some  examples  have  been  given  of  quan- 
tities of  concrete  obtained  from  certain  mixtures  of  cement,  sand, 
and  stone  in  the  laboratory,  so  that  it  will  be  of  interest  to  know 
of  some  of  the  results  in  actual  work  carried  out  on  a  large  scale. 
It  must  be  understood  that  different-sized  barrels,  different  kinds 
of  sand,  and  the  varying  amount  of  voids  in  the  broken  stone  used 
will  materially  affect  final  results. 

In  making  concrete  for  dam  No.  11  on  the  Great  Kanawha 
River  Improvement,  eleven  batches,  each  containing  2  barrels  of 
cement,  15  cubic  feet  of  sand,  and  33  cubic  feet  of  broken  stone, 
made  396  cubic  feet  or  14J  cubic  yards  of  concrete  when  rammed 
in  place.  Assuming  a  barrel  of  cement  to  be  equal  to  3.75  cubic 
feet,  this  would  make  the  proportions  by  volume  1  cement,  2  sand, 
and  4.4  broken  stone,  and  would  give  an  increase  of  concrete  over 
broken  stone  used  of  9.1  per  cent.  The  amount  of  material  used 
for  one  yard  of  concrete  was  \\  barrels  of  cement,  11J  cubic  feet  of 
sand,  and  24}  cubic  feet  of  stone. 

On  a  piece  of  work  where  1000  barrels  of  Portland  cement  was 
used  and  the  concrete  mixed  cement  1,  sand  2,  and  2^-inch  broken 
stone  4,  the  average  amount  obtained  was  20  cubic  feet  per  barrel 
of  cement.  The  broken  stone  was  well  graded  in  size,  and  the 
voids,  though  not  determined,  must  have  been  small.  This  would 
be  1.35  barrels  of  cement  for  1  cubic  yard  of  concrete. 

On  two  separate  occasions  the  author  had  accurate  records  kept 
on  street  work  where  the  concrete  was  mixed  by  machine  in  the 
proportion  of  1:2:4,  and  in  one  case  97  barrels  of  cement  made 
81  cubic  yards,  and  in  the  other  106  barrels  of  cement  made  87 
cubic  yards  of  concrete,  or  almost  exactly  1.20  barrels  of  cement 
per  cubic  yard.  In  these  particular  cases  the  parts  of  sand  and  stone 
were  taken  with  the  loose  cement  as  a  unit. 

The  author  once  laid  a  quantity  of  concrete  mixed  1:2:5  in 
a  shape  and  place  where  it  was  difficult  to  get  exact  measurements, 
and  he  was  allowed  by  the  engineers  in  charge  ten  per  cent  in  ex- 
cess- of  broken  stone  used. 


132        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

In  the  discussion  of  the  paper  before  the  American  Society  of 
Civil  Engineers,  "On  the  Theory  of  Concrete"  previously  referred 
to,  Mr.  Allen  Hazen  gives  some  data  on  concrete  mixed  under 
his  direction  as  follows:  One  barrel  of  cement,  30  pounds  of 
water,  11.4  cubic  feet  of  sand,  and  19  cubic  feet  of  gravel.  The 
volume  produced  from  the  above  was  22.7  cubic  feet,  or  an  increase 
in  concrete  over  the  gravel  of  about  20  per  cent.  On  the  entire 
work  15,085  cubic  yards  of  concrete  required  18,584  barrels  of 
cement,  or  1.23  barrels  per  cubic  yard. 

The  increase  in  the  consumption  of  cement,  both  Portland  and 
natural,  in  the  last  ten  years  has  been  something  enormous.  This 
has  been  caused  by  two  reasons.  In  the  great  amount  of  construc- 
tion work  that  has  been  going  on  natural  cement  has  taken  the 
place  of  lime  to  a  great  extent,  and  Portland  is  now  largely  used 
instead  of  natural.  This  has  been  possible  on  account  of  the  new 
and  improved  methods  of  manufacture,  so  that  both  kinds  have 
been  sold  at  largely  reduced  prices.  American  engineers,  always 
skeptical,  were  very  loath  to  try  American  Portlands,  not  believing 
that  it  could  be  made  in  this  country  equal  to  the  imported.  This 
fact,  however,  has  been  plainly  demonstrated,  and  now  American 
Portlands  are  not  only  admitted,  but  are  very  properly  called  for, 
in  a  great  many  specifications  for  important  works.  As  a  result, 
new  factories  have  sprung  up,  old  ones  have  increased  their  capaci- 
ties, and  still  in  the  last  few  years  the  demand  has  been  far  in 
advance  of  the  supply,  and  the  work  of  increase  is  going  on. 

In  the  bulletin  issued  by  the  United  States  Geological  Survey 
on  "  The  Production  of  Cement  in  1898  "  it  is  said  that  all  indica- 
tions point  to  a  large  increase  in  1899  and  an  enormous  one  in  1900; 
also  that  four  factories  in  the  Lehigh  Valley  region  will  soon  add 
1000  barrels  per  day  to  the  product  of  each,  and  it  is  claimed  that 
one  factory,  already  the  largest  in  the  world,  will  soon  reach  a  pro- 
duction of  10,000  barrels  per  day.  A  new  producing  region  has  come 
into  the  field  of  Portland-cement  production — that  of  La  Salle, 
Illinois. 

Table  No.  40  contains  an  analysis  of  the  ingredients  proposed 
to  be  used  by  one  of  the  companies  now  erecting  a  plant  at  that 
place. 


CEMENT,  CEMENT  MORTAR,  AND   CONCRETE. 


133 


TABLE  No.  40. 


LIMESTONE. 

Per  cent. 

Calcium  carbonate 88.16 

Magnesium  carbonate 1.78 

Silica 8.20 

Iron  oxide 
Alumina 


1.30 


CLAY. 

Per  cent. 

Silica 54.30 

Alumina 19.33 

Iron 5.57 

Lime 3.29 

Magnesia 2.57 

Sulphur 2.36 


Table  No.  41  shows  the  composition  of  the  ingredients  to  be 
used  in  the  manufacture  of  Portland  cement  in  Kentucky. 


TABLE  No.  41. 


LIMESTONE. 

Per  cent. 

Calcium  carbonate 97.63 

Magnesium  carbonate 0.65 

Silica 0.49 

Alumina Trace 

Iron  oxide 0.22 

Sulphuric  acid 0.34 


CLAY. 

Per  cent. 

Silica 55.82 

Iron  oxide 6. 19 

Alumina 19.77 

Lime 0.70 

Loss,  alkalies,  etc 19.52 


Table  No.  42  shows  the  domestic  production  in  barrels,  and  the 
imports  of  Portland  cements,  for  comparison. 


TABLE  No.  42. 


1890. 

1891. 

1893. 

1894. 

1895. 

1896. 

1897. 

1898. 

Home  product  
Imported  

335,500 
1,900,000 
2,235,500 

454,813 
2,988,313 
3,448,126 

590,652 
2,674,149 
3,264,801 

798,75? 
2.638,107 
3,436,864 

990,324 
2,997,395 
3,988,719 

1.543,023 
2,989,597 
4,532,620 
85,486 
4,447,134 

2,677,775 
2,090,924 
4,768,699 
53,466 
4,715,233 

3,692,284 
2,013,818 
5,706,102 
36,732 
5,669,370 

Total         

Consumption 

It  can  readily  be  seen  how  strong  a  hold  American  Portlands 
have  on  the  market,  when  from  1896  to  1898  the  imports  fell  off 
975,779  barrels  and  the  domestic  production  increased  2,149,261 
barrels.  The  value  of  the  domestic  product  for  1898  was  $5,970,- 
773,  or  about  $1.62  per  barrel. 

Table  No.  43  shows  the  amount  of  American  natural  cement 
produced  from  1893  to  1898  inclusive,  and  also  the  consumption 
of  all  kinds  of  cement  for  the  same  time  in  barrels. 


134        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

TABLE  No.  43. 


\ 

American  Natural. 

Total  Consumption. 

1893 

7,411,815 

10,676,616 

1894 

7,563,488 

11,000,352 

1895 

7,741,077 

11,728,796 

1896 

7,970,450 

12,503,070 

1897 

8,311,688 

13,080,387 

1898 

8,418,924 

14,125,026 

A  barrel  is  assumed  to  contain  300  pounds  of  natural  or  380 
pounds  of  Portland  cement. 

The  total  value  of  the  natural  product  for  1898  was  $3,888,728, 
or  $0.46  per  barrel. 


CHAPTER   VI. 

THE   THEORY   OF   PAVEMENTS. 

LORD  MACATJLAT  said  in  his  History  of  England:  "  Of  all  in- 
ventions, the  alphabet  and  printing-press  alone  excepted,  those  in- 
ventions which  abridge  distance  have  done  most  for  the  civilization 
of  our  species." 

Adam  Smith  once  asserted  that  "  the  construction  of  roads  is 
the  greatest  of  all  improvements."  While'  these  remarks  Had 
special  reference  to  communication  between  towns  or  villages, 
they  can  with  equal  force  be  applied  to  cities  and  towns  themselves. 
Some  one  has  said:  "Tell  me  the  condition  of  the  churches  of  a 
city,  and  I  will  tell  you  of  the  prosperity  of  that  city."  If  this 
be  true  of  churches,  how  much  more  truly  can  it  be  said  of  the 
pavements!  Probably  no  one  condition  in  a  city  strikes  a  stranger 
as  forcibly  as  the  general  appearance  of  its  streets.  The  clean  and 
improved  pavements  of  New  York  City  during  the  last  few  years 
have  impressed  the  rural  visitor  more  than  any  one  other  feature 
of  the  city,  the  tall  office-buildings,  even,  not  excepted. 

The  word  "  pavement "  comes  from  the  Latin  pavimentum  and 
means  "  a  floor  rammed  or  beaten  down  ";  hence  the  hard  smooth 
surface  of  a  street  can  be  called  pavement.  It  can  be  defined  as 
the  artificial  surface  of  an  improved  roadway  formed  of  hard  or 
durable  material  for  the  purpose  of  facilitating  travel  and  forming 
a  presentable  surface  to  a  street  at  all  seasons  of  the  year. 

There  has  been  considerable  discussion  among  engineers  as  to 
what  really  constitutes  a  pavement.  Its  importance  can  be  seen 
when  it  is  remembered  that  a  great  many  cities  compel  abutting 
property  owners  to  pay  for  the  first  pavement,  but  keep  it  in  repair 
and  renew  it  at  the  expense  of  the  city  at  large.  The  people,  know- 
ing this,  often  make  their  first  improvement  as  cheaply  as  possible, 

135 


136        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

leaving  to  the  general  public  the  task  of  effecting  a  real  and  perma- 
nent improvement. 

Pavements  have  been  laid  of  many  materials,,  both  perishable 
and  imperishable,  natural  and  artificial.  The  experience  of  one 
city  has  not  seemed  to  benefit  very  greatly  any  other,  but  it  has 
seemed  necessary  for  each  one  to  work  out  the  problem  for  itself. 
This  was  especially  true  in  earlier  years,  when  there  was  less  com- 
munication between  city  officials  and  when,  too,  there  was  less  in- 
terest taken  in  the  subject.  At  the  present  time  the  ideas  of  city 
officers  are  spread  abroad  through  the  medium  of  official  reports, 
technical  societies,  and  technical  journals,  so  that  one  can  easily 
know  what  is  being  done  in  outside  cities  by  keeping  in  touch  with 
these  means  of  communication. 

But  it  by  no  means  follows  that  the  decision  as  to  what  is  the 
best  paving  material  for  one  locality  will  necessarily  govern  in  an- 
other, however  intelligently  it  may  have  been  reached.  There  are 
so  many  conditions  affecting  this  question  that  it  must  generally 
be  decided  by  their  careful  study  in  each  particular  case.  For  in- 
stance, stone  may  from  its  proximity  and  availability  be  just  the 
material  for  one  city  and  the  cost  of  transportation  make  it  pro- 
hibitive for  another,  and  some  other  material  must  be  used. 

The  value  of  pavements  to  a  city  or  a  particular  neighborhood 
is  positive  and  immediate.  Real-estate  owners,  than  whom  no  more 
shrewd  or  sagacious  men  are  in  business,  recognize  this,  and  when 
they  wish  to  put  a  piece  of  property  on  the  market  at  once  and  at 
good  prices,  always  pave  the  streets  with  the  most  popular  material. 
The  pavement  improves  the  appearance  of  the  streets  so  much  that 
the  lots  not  only  sell  more  rapidly,  but  the  owner  can  add  to  his 
price  more  than  enough  to  reimburse  him  for  his  outlay. 

Of  how  much  importance  street  pavements  are  in  a  large  city- 
can  be  understood  only  by  a  knowledge  of  their  cost  and  extent. 
In  the  present  city  of  New  York  there  were  1720  miles  of  pave- 
ments on  January  1,  1900.  Assuming  the  cost  of  a  good  pavement 
to  be  $2.25  per  yard  and  the  average  width  of  a  street  to  be  30  feet 
between  curbs,  the  cost  per  mile,  including  curbing,  will  be 
about  $50,000,  making  a  total  of  $86,000,000  New  York  City  would 
have  invested  if  her  street  pavements  were  all  of  good  character  and 
in  good  condition.  Or  assuming  that  each  street  must  be  repaved 


THE  THEORY  OF  PAVEMENTS.  13T 

every  twenty-five  years,  to  keep  the  above  mileage  renewed  when 
worn  out  will  require  the  laying  of  69  miles  of  street  pavement  each 
year.  Assuming  further  that  the  average  cost  of  repairs  to  all 
pavements  will  be  nothing  for  the  first  five  years,  and  three  cents 
per  yard  for  the  remainder  of  its  life,  the  total  annual  expense  for 
maintenance  and  repairs  on  the  present  mileage  of  New  York 
City's  pavements  will  be  $528  per  mile,  or  $690,096  for  repairs  and 
$3,450,000  for  renewals,  or  avsum  total  of  $4,140,096  per  annum  to 
keep  the  present  paved  streets  of  New  York  in  good  condition. 
Other  cities  will  have  less  cost,  but  this  illustration  shows  the 
necessity  of  careful  study  and  investigation. 

It  will  be  of  interest  and  value  to  know  how  these  vast  sums 
are  raised;  and  while  payments  for  all  public  improvements  must 
come  from  the  property  owner,  the  methods  of  obtaining  it  vary 
much  in  their  detail. 

In  a  paper  called  "  Theory  and  Practice  of  Special  Assess- 
ments" read  before  the  American  Society  of  Civil  Engineers  by 
Mr.  J.  L.  Van  Ornum,  the  methods  of  paying  for  street  improve- 
ments in  fifty  cities  were  given.  Table  No.  44  is  compiled  from  this 
paper. 

When  special  assessments  are  made  against  the  abutting  prop- 
erty different  methods  are  adopted  for  payments.  In  certain  sec- 
tions of  the  West  the  tax  is  due  in  instalments,  special  bonds  being 
issued  to  raise  funds  to  pay  the  contractor,  which  bonds  mature 
as  the  instalments  are  paid,  and  are  not  considered  as  a  general 
indebtedness  against  the  city. 

In  other  places  the  entire  amount  is  payable  when  the  work  is- 
completed,  tax  certificates  against  the  property  being  issued  to  the- 
contractor  as  payment,  and  he  being  compelled  to  make  all  col- 
lections. In  the  East  it  is  more  common  to  make  the  tax  payable- 
after  work  is  completed  and  assessment  laid,  funds  being  provided 
temporarily  by  the  issue  of  stock  of  the  city. 

When  the  amount  of  money  involved  is  so  great,  it  is  not  strange- 
that  many  inventors  have  been  at  work  and  many  experiments  made- 
to  determine  what  is  the  best  material  for  pavements.  As  a  result 
streets  have  been  paved  with  stone  in  varied  forms  and  shapes,, 
wood,  asphalt,  coal-tar,  cement  concrete,  iron,  brick,  india-rubber,, 
shells,  gravel,  slag  blocks,  and  even  glass  and  hay;  and  many  of 


138        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


these  in  such  modified  ways  as  to  make  entirely  different  pave- 
ments. 

TABLE  No.  44. 


City. 

Grading,  how  paid. 

Original  paving, 
how  paid. 

Repaving,  how  paid, 

Atlanta  Ga.         .... 

By  city  at  large 

%  by  abutting  prop- 

% by  abutting  prop- 

Baltimore, Md  
Boston,  Mass  

All  by  abutting  prop- 
erty owners 
All  by  abutting  prop- 

erty owners,   ^  by 
city  at  large 
All  by  abutting  prop- 
erty owners 
All  by  abutting  prop- 

erty   owners,    \fa    bv 
city  at  large 

All  by  city  at  large 

Cincinnati   O 

erty  owners 
2%   by  city  at  large 

erty  owners 
2%  by  city  at  large  98$ 

Indianapolis,  Ind... 
Louisville,  Ky  

98£       by       abutting 
property  owners 
All  by  abutting  prop- 
erty owners 
All  by  abutting  prop- 

by   abutting    prop- 
erty owners 
All  by  abutting  prop- 
erty owners 
All  by  abutting  prop- 

when done   by  spe- 
cial act  of  legislature 
All  by  abutting  prop- 
erty owners 
By  city  at  large 

Milwaukee  Wis 

erty  owners 
All  by  abutting  prop- 

erty owners 
All  by  abutting  prop- 

By the  ward    except 

Minneapolis,  Minn  .  . 
Newark  N  J.     .. 

erty  owners,  except 
intersections,  which 
are  for  paid  for  by 
city  at  large 
By  the  ward 

All  by  abutting  prop- 

erty owners,  except 
intersections,  which 
are  for  paid  for  by 
city  at  large 
By  the  abutting  prop- 
erty owners,  except 
intersections,  which 
are  paid  for  by  city 
All  by  abutting  prop- 

when   on    concrete 
foundation,  then  as 
original       improve- 
ment 
By  the  abutting  prop- 
erty owners,  except 
intersections,  which 
are  paid  for  by  city 
All  by  abutting  prop- 

New Orleans,  La.  .  .  . 

New  York  City  
Omaha,  Neb  

erty  owners 
%  by  abutting  prop- 
erty, J4  by  city  at 
large 
All  by  abutting  prop- 
erty owners 
%  by  abutting  prop- 

erty owners 
%  by  abutting  prop- 
erty owners,   J4    by 
city  at  large 
All  by  abutting  prop- 
erty owners 
All  by  abutting  prop- 

erty owners 
%  by  abutting  prop- 
erty   owners,  £4  by 
city  at  large 
By  city  at  large 

All  by  abutting  prop- 

Philadelphia, Pa  — 

erty   owners,  &j  by 
city  at  large 

By  city  at  large 
All  by  abutting  prop- 

erty owners,  except 
intersections,  which 
are  paid  for  by  city 
at  large 
All  by  abutting  prop- 
erty owners 
All  by  abutting  prop- 

erty owners,  except 
intersections,  which 
are  paid  for  by  city 
at  large 
By  city  at  large 

All  by  abutting  prop- 

St. Louis,  Mo  

erty  owners 
By  city  at  large 

erty  owners 
All  by  abutting  prop- 
erty owners 

erty  owners 
All  by  abutting  prop- 
erty owners 

Durability  was  thought  to  be  of  great  importance,  and  iron 
was  experimented  with  in  several  cities.  It  was  once  tried  in  St. 
Louis,  but  was  soon  taken  up. 

Iron  blocks  laid  on  Cortlandt  Street,  New  York,  about  1865, 
were  roughened  on  the  surface  by  hexagonal  projections  about  one 
inch  in  size,  separated  by  similar  depressions.  This  made  a  rough 
and  noisy  pavement;  horses  tore  off  their  shoes,  slipped  and  fell 
frequently;  so  that  after  a  short  trial  it  was  taken  up  and  replaced 
with  stone. 

In  1885  some  one  suggested  a  hollow  iron  block  4  inches  wide 


t 
THE  THEORY  OF  PAVEMENTS.  139 

and  from  10  to  12  inches  long,  the  hollow  to  be  filled  with  any  ma- 
terial that  might  seem  fit. 

In  1877  "iron  paving"  was  laid  on  "  Unter  den  Linden"  in 
Berlin.  It  remained  for  quite  a  number  of  years,  being  removed 
about  1890  at  the  request  of  the  experimenters.  The  same  people, 
however,  continued  their  work  by  paving  the  intersection  of 
Langen-Strasse  and  Marcus-Strasse  with  impregnated  wooden 
blocks  capped  with  steel.  The  blocks  were  laid  on  concrete,  and 
the  joints  filled  with  a- bituminous  preparation.  An  inquiry  as  to 
this  pavement  in  1899  elicited  the  following  reply: 

"  The  pavement  which  was  laid  down  in  the  year  1888  by  the 
United  Kb'nigs-  and  Laura-IIiitte  in  the  Langen-Strasse  at  the 
junction  of  Marcus-  and  Holzmarkt-Strasse  was  removed  in  the 
summer  of  the  year  1897,  upon  application  of  the  makers,  and  has 
been  replaced  by  asphalt  pavement. 

"  Although  the  pavement  had  shown  itself  to  be  pretty  durable 
in  the  beginning,  it  was,  after  an  existence  of  about  eight  years, 
so  worn  out  in  its  steel-capping  in  consequence  of  the  heavy  traffic, 
that  it  required  a  renewing  of  the  latter,  and  an  entire  repavement 
became  necessary. 

"  As  from  the  beginning  the  building  administration  on  ac- 
count of  the  very  high  price — about  twice  as  much  as  for  asphalt 
pavement — doubted  the  wisdom  of  granting  a  further  appliance  of 
this  wood-iron  pavement,  the  company,  who,  as  the  party  obliged 
to  keep  the  pavement  in  good  order,  would  have  had  to  carry  the 
cost  of  renewing,  asked  us  to  be  relieved  of  this  obligation. 

"  This  request  was  granted  by  us,  and  as  already  stated  above, 
after  removal  of  the  wood-iron  pavement  the  same  was  replaced  by  a 
pounded  asphalt  pavement. 

"  It  is  hardly  necessary  to  mention  that  the  cost  of  the  pave- 
ment in  question  would  have  been  considerably  increased  by  the 
present  price  of  iron,  which  is  almost  100  per  cent  higher  than  it 
was  at  that  time/' 

Another  plan  was  to  set  hollow  iron  cylinders  closely  together 
on  a  firm  base  and  fill  all  interstices  as  well  as  the  cylinders  with 
concrete,  the  idea  being  that  the  iron  would  prevent  the  wear,  and 
the  concrete  a  general  smoothness.  It  is  doubtful  if  this  idea  was 
ever  experimented  with,  even. 


14:0        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

In  1890  a  small  piece  of  experimental  pavement  was  laid  on  a 
sidewalk  crossing  in  Columbus,  0.,  at  an  entrance  to  a  railroad 
freight-yard.  An  iron  plate  was  cast  with  pockets  37/16  inches 
square  on  the  upper  side.  Each  plate  contained  five  full,  four  half, 
and  four  quarter  pockets  so  arranged  that  when  set  on  the  street 
the  plates  were  square  and  the  pockets  at  an  angle  of  45°  with  the 
length  of  the  street.  The  plates  were  bedded  on  the  foundation, 
and  into  the  pockets  were  driven  oak  blocks  five  inches  high  and 
projecting  two  inches  above  the  pockets.  At  the  end  of  sixteen 
months  the  blocks  showed  a  wear  of  but  J  inch,  when  it  is  said 
that  macadam  within  the  freight-yard  was  renewed  in  ninety  days, 
and  asphalt  outside  was  replaced  in  four  months.  This  pavement 
would  hardly  be  practicable,  however,  on  a  large  scale. 

About  1889  a  so-called  jasperite  pavement  was  laid  in  Wichita, 
Kansas,  the  process  being  protected  by  letters  patent.  It  con- 
sisted simply  of  a  concrete  made  of  Portland  cement  and  the  par- 
ticularly hard  stone  found  near  Sioux  Falls,  South  Dakota.  The 
author  talked  at  the  time  with  the  patentee,  who  was  quite  enthusi- 
astic over  his  contract.  The  work  amounted  to  several  thousand 
yards,  but  never  was  a  success,  and  was  not  repeated  anywhere 


About  1898  an  experimental  pavement  of  compressed  marsh- 
grass  was  tried  in  Eichmond,  Va.  The  grass  was  first  treated  with 
a  preparation  of  oil,  tar,  and  resins,  and  then  compressed  with 
hydraulic  pressure  into  blocks  about  5  inches  square  and  bound 
together  with  wire.  The  blocks  were  laid  in  the  usual  way  on  a  street 
where  they  were  subjected  to  very  heavy  traffic.  The  pavement 
lasted  but  a  few  months. 

A  pavement  that  is  somewhat  used  in  England  where  the  traffic 
is  light  is  called  "  tar-macadam." 

A  10-inch  bed  of  hard  clinkers  and  broken  stone  is  well  rolled 
with  a  12-ton  steam-roller  and  covered  with  4  inches  of  2^-inch 
broken  stone  well  rolled.  Upon  this  is  laid  a  3-inch  course  of  tar- 
macadam,  consisting  of  one  ton  of  IJ-inch  granite  to  12  gallons  of 
tar,  28  pounds  of  pitch,  and  2  gallons  of  creosote  oil.  This  is  well 
rolled  and  covered  with  an  inch  of  limestone  screenings  mixed  with 
the  same  cementing  material,  then  covered  with  fine  screenings 
and  again  rolled. 


THE  THEORY  OF  PAVEMENTS.  141 

In  certain  portions  of  Germany  a  combination  iron  macadam  is 
used  for  roadways.  Common  iron  slag  treated  so  as  to  lose  some  of 
its  brittleness  is  broken  into  small  pieces  as  nearly  uniform  as  pos- 
sible. It  is  then  spread  over  the  surface  of  the  road  and  thoroughly 
rolled.  Bog  iron-ore  is  then  scattered  over  it  until  it  is  covered, 
and  the  whole  mass  again  rolled  to  a  hard  surface.  Where  the 
traffic  is  heavier,  broken  stone  is  used  over  the  slag. 

Artificial  stone  blocks  have  been  made  in  Chemnitz  as  follows: 
Coal-tar  is  mixed  with  sulphur  and  warmed  thoroughly.  Chlorate 
of  lime  is  added  to  the  resulting  semi-liquid  mass.  After  being 
allowed  to  cool,  it  is  broken  into  small  pieces  and  mixed  with  glass 
or  blast-furnace  glass  slag.  The  entire  mixture  is  then  subjected 
to  a  pressure  of  200  atmospheres  and  reduced  to  whatever  form  or 
shape  is  desired.  Its  specific  gravity  is  2.2.  Its  crushing  strength  is 
143  kilograms  to  the  square  centimeter.  Its  durability  is  con- 
sidered to  be  about  one-half  of  Swedish  granite.  It  makes  a  pave- 
ment easily  cleaned,  and  is  said  not  to  be  slippery. 

In  1898  an  experimental  pavement  was  laid  in  Lyons,  France. 
It  was  made  of  blocks  of  devitrified  glass.  The  blocks  were  eight 
inches  square,  each  one  being  cut  on  top  into  sixteen  smaller 
squares,  so  that  the  finished  pavement  looks  very  much  like  a  huge 
checker-board. 

The  treatment  consists  in  heating  broken  glass  to  a  temperature 
of  1250°  and  compressing  it  into  moulds  by  hydraulic  force.  The 
physical  transformation  of  the  glass  is  due  to  devitrification  under 
the  Garchy  process.  This  action,  however,  is  more  apparent  than 
real,  as  a  chemical  analysis  shows  that  after  devitrification  the 
glass  has  the  same  composition  as  before.  It  possesses  all  intrinsic 
qualities  of  glass  except  transparency.  It  will  also  resist  crushing, 
and  heavy  frosts,  very  much  better  than  before  treated. 

In  a  pavement  it  is  said  to  have  greater  resistance  than  stone, 
is  a  poor  conductor  of  heat,  so  that  ice  will  not  readily  form  upon 
it,  it  is  easily  cleaned,  and  is  sanitary.  It  is  considered  to  be  more 
durable  than  stone  and  just  as  cheap. 

Portland  cement  has  been  used  in  street  pavements  in  Belle- 
fontaine,  0.,  to  a  considerable  extent.  It  was  first  tried  there  in 
1884,  and  the  streets  so  paved  were  in  a  fair  condition  after  fifteen 
years  of  service.  The  City  Engineer  in  writing  of  them  says: 


142        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

"  The  greatest  objection  is  that  they  are  slippery.  Very  few  people 
here  now  advocate  their  construction,  brick  and  asphalt  having 
the  preference." 

These  pavements  were  laid  on  a  4-inch  base  formed  of  one  part 
of  the  best  Portland  cement  and  four  parts  of  gravel  and  sand 
about  equally  mixed.  This  was  made  into  a  concrete  and  thor- 
oughly tamped  on  the  street.  Upon  this,  and  before  it  was  set,  was 
spread  the  top  course  2  inches  thick,  composed  of  one  part  of 
cement  as  above  and  one  part  of  sand  and  gravel  sifted  to  the  size 
of  a  pea,  a  very  thin  layer  of  neat  cement  mortar  being  rubbed  into 
the  concrete  to  insure  a  good  bond  between  the  two  layers. 

Both  layers  were  separated  into  blocks  5  feet  square  and  the 
surfaces  grooved  into  4-inch  squares,  these  grooves  being  V-shaped 
and  3/ie  inch  deep  and  1  inch  wide. 

When  completed  the  entire  surface  was  covered  with  2  inches 
of  wet  sand  and  kept  in  that  condition  for  one  week. 

In  New  Orleans  roadways  of  streets  have  been  improved  with 
shells.  Oyster-shells  are  first  spread  over  the  roadway  to  a  depth 
sufficient  to  give  6  inches  when  consolidated  and  then  thoroughly 
rolled.  Upon  this  another  6-inch  layer  of  lake  shells  is  placed  and 
also  rolled.  This  gives  a  nice,  smooth,  pleasing  surface  for  light 
driving,  but  of  course  would  not  stand  heavy  traffic. 

Another  form  of  improvement  is  made  of  chert.  Chert  is  a 
sort  of  disintegrated  granite  common  in  some  parts  of  the  South 
and  possessed  of  a  cementing  property,  after  having  been  wet  and 
rolled,  that  makes  a  hard,  smooth  surface  upon  a  street.  In  New 
Orleans  the  subgrade  is  first  covered  with  1  x  12-inch  cypress 
planks.  The  material  is  then  spread  in  a  6-inch  layer,  sprinkled  and 
rolled.  Other  layers  3  inches  in  thickness  are  added  till  the  re- 
quired depth  of  material  is  obtained.  This  makes  a  cheap  and  good 
roadway.  The  object  of  the  planks  is  to  prevent  the  chert  from 
being  rolled  into  the  soft  soil,  and  its  moist  condition  should  pre- 
vent the  decay  of  the  wood. 

In  the  early  eighties  an  artificial  pavement  called  the  Pelletier 
block  was  used  in  Chicago.  It  consisted  of  any  hard  stone,  crushed 
and  thoroughly  dried,  and  then  mixed  with  ten  per  cent  of  iron 
slag  or  low-grade  ore.  It  was  then  subjected  to  a  thorough  in- 
fusion of  a  chemical  combination  of  oxide  and  chloride  of  iron 


THE  THEORY  OF  PAVEMENTS.  143 

which  was  intended  to  act  as  a  perpetual  binder,  growing  harder 
and  firmer  with  age  and  exposure  to  the  weather.  These  blocks 
were  subjected  to  great  pressure  during  manufacture,  and  were 
impervious  to  water.  They  were  never  very  much  used. 

In  Cairo,  Egypt,  an  attempt  was  made  to  form  a  street  surface 
by  pouring  hot  asphalt  over  a  bed  of  broken  stones.  But  the  re- 
sults were  not  satisfactory. 

Later  another  experiment  was  tried  by  making  slabs  of  bitumi- 
nous asphalt  concrete  by  mixing  natural  liquid  asphalt  with  or- 
dinary broken  stone,  and  then  laying  a  pavement  with  the  slabs. 
This  was  but  a  partial  success. 

Between  Valencia  and  Grao  in  Spain  there  has  been  a  stone- 
paved  roadway  for  some  years.  About  1890  a  trial  was  made  of 
laying  flat  steel  rails  in  the  wheel-tracks.  The  rails  are  laid  double 
in  the  natural  soil  with  no  special  foundation.  Where  they  join 
a  slight  indentation  is  made  so  that  wheels  will  more  readily  keep 
the  tracks.  The  rails  are  kept  in  gauge  by  steel  cross-bars  spaced 
at  proper  intervals. 

After  the  tramway  had  been  in  use  for  seven  years  the  average 
annual  cost  for  repairs  had  been  $380,  while  previously  the  stone 
pavements  required  on  outlay  of  $5470  per  annum,  or  a  net  saving 
for  repairs  of  $5090  each  year,  or  for  the  seven  years  a  total  of 
$35,630,  while  the  entire  cost  of  the  iron  track  was  only  $28,518. 
The  average  traffic  on  the  road  was  3200  vehicles  per  day.  A  charge 
of  8/io  of  a  cent  is  levied  for  each  vehicle. 

In  1875  experiments  were  made  in  Budapest  with  a  view  of 
making  paving-blocks  of  ceramite.  By  1878  they  had  been  pro- 
duced with  a  crushing  strength  of  from  27,000  to  43,000  Ibs.  per 
square  inch.  They  were  then  adopted  as  a  paving  material,  being 
4x4x8  inches  in  size.  The  method  of  laying  was  to  form  the 
natural  soil  of  the  street  into  the  desired  shape  and  lay  on  it  flat- 
wise bricks  3J  x  4  x  11 J  inches.  The  joints  of  this  first 'course  were 
filled  with  cement  mortar.  A  cushion  of  sand  0.8  inch  thick  was 
spread  over  the  entire  surface  and  the  ceramite  blocks  laid  upon  it. 
The  blocks  were  laid  with  0.4-inch  joint  filled  with  a  composition 
of  1  part  coal-tar,  1  part  pitch,  and  from  15  to  20  parts  of  sand 
according  to  fineness.  The  blocks  weighed  22  pounds  each.  No 
description  of  the  method  of  manufacturing  or  material  of  these 


144        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

"blocks  could  be  'obtained,  but  from  their  name  they  probably  were 
burned  brick  of  especially  prepared  clay. 

The  following  is  a  description  of  a  patented  noiseless  stone  pave- 
ment: Granite  blocks  5x3  inches  are  wrapped,  except  the  upper 
surface,  with  waste  fibre  and  an  elastic  bituminous  compound,  and 
the  whole  brought  together  while  resting  on  a  continuous  pad  of 
the  same  material.  The  pad  is  taken  to  the  street  and  unrolled 
over  the  concrete.  The  blocks  are  set  diagonally  and  by  a  power- 
ful lever  pressed  firmly  together.  This  was  claimed  to  make  a 
smooth,  noiseless,  and  sanitary  pavement. 

In  1896  a  space  9x9  feet  was  cut  out  of  an  asphalt  pavement 
in  Topeka,  Kansas,  and  then  paved  up  with  blocks  of  compressed 
wood  pulp  six  inches  square  and  four  inches  deep.  This  was  sub- 
jected to  a  wear  of  about  720  vehicles  per  day.  At  the  end  of  two 
weeks  the  wear  was  perceptible,  but  was  not  very  extensive  till  at 
the  end  of  four  months,  when  the  blocks  wore  so  rapidly  that  they 
had  to  be  taken  up.  On  account  of  the  wear,  the  asphalt  was  so 
broken  near  them  that  the  original  space  of  9x9  feet  had  become 
11  x  16  feet  which  required  repaving. 

A  few  years  ago  a  novel  pavement  was  laid  in  Oakland,  Cal.  It 
was  a  combination  of  wood  and  asphalt.  The  base  was  the  usual 
cement  concrete  6  inches  thick.  Upon  this  foundation  were  laid 
redwood  blocks  6  inches  square  and  4  inches  deep.  The  blocks  were 
submerged  in  a  bath  composed  of  80  per  cent  of  hard  asphalt  and  20 
per  cent  of  liquid  flux  for  about  five  minutes.  It  was  found  that 
the  time  of  immersion  did  not  affect  the  penetration  of  the  asphalt 
as  much  as  the  temperature  of  the  bath,  which  was  kept  from  350° 
to  400°  to  get  satisfactory  results.  Previous  to  the  block-laying, 
the  concrete  was  given  a  thin  coating  of  liquid  asphalt  at  a  boiling 
temperature,  although  it  is  admitted  that  it  is  doubtful  if  its  utility 
justified  the  expense.  It  was  done  as  an  extra  precaution  to  keep  as 
much  moisture  as  possible  from  the  wood. 

1  The  blocks  were  laid  close  at  right  angles  to  the  street.  The 
joints  were  then  filled  with  a  grouting  material  composed  of  80 
parts  of  hard  and  20  parts  of  liquid  asphalt  and  30  parts  of  car- 
bonate of  lime,  being  first  mixed  with  15  parts  of  liquid  asphalt. 
The  grouting  was  applied  at  three  different  times,  so  that  all  the 
joints  should  be  filled  and  the  blocks  covered  with  about  J  inch  of 


THE  THEORY  OF  PAVEMENTS.  145 

asphalt.  A  coating  of  sand  about  J  inch  thick  is  then  spread  over 
the  entire  surface.  This  sand  is  gradually  absorbed  by  the  asphalt, 
which  thus  becomes  hard  and  firm,  leaving  the  wood  coated  with 
4  inch  of  what  is  very  similar  to  bituminous  rock. 

The  grout  when  cold  is  said  to  hold  the  blocks  together  with  a 
strength  of  200  pounds  per  square  inch.  The  asphalt  covering  is 
supposed  to  be  only  a  carpet  to  carry  the  load  that  is  really  sup- 
ported by  the  blocks.  Its  durability  will  be  according  to  the  traffic, 
but  under  conditions  in  a  city  like  Oakland  it  is  expected  to  last 
two  or  three  years,  when  it  must  be  renewed.  The  cost  of  renewal 
is  about  4J  cents  per  square  yard.  No  expansion  joints  were  left, 
as  it  was  supposed  that  all  absorption  of  moisture  had  been  pre- 
vented by  the  asphalt  bath.  With  proper  renewals  of  the  covering 
this  pavement  is  supposed  to  last  almost  indefinitely,  as  the  asphalt 
treatment  of  the  redwood  should  prevent  decay  except  after  a  very 
long  time. 

The  Jetley  pavement  of  London  is  thus  described:  "Under 
this  system  the  wood  blocks  are  compressed  and  combined  very 
powerfully  together  by  machinery  and  in  such  a  manner  that  no 
block  can  afterwards  move,  and  it  is  brought  ready  made  to  the 
street  which  is  to  be  laid,  in  slabs  4'  6"  x  12"  wide,  and  when  the 
roadway  is  completed  it  forms  a  homogeneous  structure  from  curb 
to  curb  so  powerful  that  no  block  can  move  and  consequently  will 
remain  perfectly  level." 

The  slabs  are  laid  without  concrete,  and  when  worn  rough  are 
turned  over,  giving  practically  a  new  pavement.  After  three  years' 
service  a  pavement  of  this  character  was  said  to  have  been  as  smooth 
as  when  first  laid. 

These  examples  show  how  varied  have  been  the  attempts  to  find 
the  best  methods  of  improving  streets  and  roads.  They  cannot 
all  be  said  to  have  been  failures,  nor,  if  they  had,  would  they  be 
without  value.  Mankind  as  a  whole,  and  engineers  in  particular, 
should  learn  by  mistakes  of  their  fellows  as  well  as  by  their  suc- 
cesses. 

The  question  as  to  what  is  the  best  material  for  street  pave- 
ments, and  the  detailed  methods  in  which  it  shall  be  laid,  is  by  no 
means  settled  at  the  present  time.  Much  experimental  work  is 
going  on  now,  but  much  has  been  accomplished  during  the  past 


146        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

twenty  years.  At  that  time  Belgian-block  pavement  was  the  im- 
proved pavement,  and  it  composed  a  large  proportion  of  the  paved 
area  of  New  York  City.  During  the  last  ten  years  it  has  nearly 
all  been  replaced  by  asphalt  or  granite  blocks,  although  it  was  in 
good  condition.  It  makes  way  for  its  betters. 

In  Philadelphia,  in  1884,  535  miles  or  93  per  cent  of  the  pave- 
ments of  the  city  were  of  cobblestone.  Now  the  cobblestone  has  al- 
most entirely  disappeared  from  the  streets,  and  in  its  place  are  found 
granite,  asphalt,  and  vitrified  brick. 

While  many  materials  are  now  being  used  in  pavements,  it  is 
safe  to  say  that  stone,  asphalt,  and  vitrified  brick  are  the  'only 
materials  that  should  be  considered  to-day  for  street-paving  pur- 
poses. 

American  cities  have  not  seemed  in  the  past  to  have  profited 
much  by  the  customs  of  their  fellows.  During  the  past  fifty  years 
nearly  all  of  them  have  laid  their  first  street  pavements.  In  nearly 
every  instance  the  city  officials  have  worked  out  the  problem  for 
themselves.  In  some  respects  it  was  a  new  problem  in  each  place. 
The  best  material  for  New  York  was  not  necessarily  the  best  for 
Omaha,  nor  does  it  follow  that  Omaha's  selection  would  be  right 
for  cities  still  further  west.  Economic  conditions  must  always  be 
considered.  A  city,  like  an  individual,  must  be  guided  to  a  certain 
extent  by  its  financial  condition.  The  cost  of  transportation  prob- 
ably affects  a  selection  more  than  any  other  one  condition.  Wood 
is  cheap  at  Chicago,  Milwaukee,  and  Detroit  on  account  of  water 
transportation,  and,  although  of  short  life,  is  being  used  in  those 
and  some  other  Western  cities  long  after  it  has  been  given  up  in 
most  places  where  it  has  been  tried. 

Stone  has  long  been  acknowledged  as  being  the  most  economical 
material  for  Eastern  cities  that  can  be  easily  reached  by  water,  but 
its  cost  makes  it  prohibitive  to  the  large  number  of  places  in  the 
Mississippi  Valley.  Local  conditions  must  always  be  considered, 
so  that  it  is  not  possible  to  lay  down  any  fixed  rule  as  to  what 
material  makes  the  best  pavement.  But  by  a  careful  study  and 
understanding  of  what  properties  are  necessary  for  a  good  pave- 
ment, and  a  thorough  knowledge  of  the  materials  proposed,  an 
engineer  can  determine  what  selection  should  be  made  under  given 


THE  THEORY  OF  PAVEMENTS.  H7 

conditions.  Understand  the  principles  first  and  apply  them  after- 
ward. 

An  ideal  pavement  should  be  cheap,  durable,  easily  cleaned, 
present  little  resistance  to  traffic,  non-slippery,  cheaply  main- 
tained, favorable  to  travel,  and  sanitary.  Letting  the  perfect  pave- 
ment have  a  value  of  100  by  a  study  of  these  different  properties, 
it  is  possible  to  assign  to  each  its  proportional  value  of  the  whole. 

CHEAPNESS. — No  matter  how  desirable,  or  how  economical 
even,  any  material  may  be,  its  first  cost  is  a  question  of  importance 
in  deciding  upon  its  availability.  If  the  property  owners  cannot 
pay  for  it,  the  question  is  settled  at  once.  There  is  no  chance  for 
argument.  A  committee's  recommendation  is  often  rejected  when 
its  wisdom  is  not  questioned,  simply  on  account  of  the  cost.  When 
the  best  cannot  be  taken  this  phase  is  developed:  with  the  money 
available  how  can  the  best  results  be  obtained?  A  person  present- 
ing a  new  plan  or  a  new  material  will  first  be  asked  as  to  its  cost. 
And  if  it  be  expensive,  his  will  be  a  hard  task  to  have  it  receive  a 
fair  trial  except  at  his  own  expense.  Cheapness,  therefore,  has  been 
given  a  value  of  15. 

DURABILITY. — This  is  also  an  economic  property.  Upon  this 
depends  ultimate  cost,  and  in  this  connection  must  be  considered 
with  first  cost.  If  a  pavement  be  cheap,  and  pleasing  even,  it  can 
never  be  a  complete  success  if  it  has  not  durability.  Americans 
expect  any  construction  to.  care  for  itself  largely.  They  are  not 
given  to  economies  in  repairs. 

Durability,  too,  is  affected  by  so  many  varied  conditions  that  it 
is  discussed  with  difficulty.  It  is  acted  upon  principally  by  traffic 
and  the  atmosphere.  The  effect  of  the  former  depends  directly 
upon  its  quantity,  and  the  latter  upon  the  character  of  the  ma- 
terial and  the  climate  to  which  it  is  exposed.  For  instance,  wood 
will  have  only  a  certain  life  even  if  it  sustain  no  traffic  whatever, 
while  stone  or  good  brick  would  last  practically  forever  under  the 
same  conditions.  Asphalt  also  is  somewhat  affected  by  the  air,  but 
not  to  such  an  extent  as  wood. 

The  influence  of  traffic  is  modified  by  five  principal  conditions, 
viz.,  width  of  roadway,  character  of  pavement,  presence  or  absence 
of  street-car  track,  state  of  repairs,  and  how  well  the  pavement  is 
cleaned.  Traffic  has  been  measured  in  this  country  by  counting 


14:8        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

the  number  of  vehicles  passing  over  a  street  in  a  given  time,  and 
so  arrive  at  an  approximate  tonnage  without  regard  to  width.  In 
England  efforts  have  been  made  to  arrive  at  more  definite  results, 
and  the  tonnage  per  yard  of  width  of  roadway  per  day  or  year  has 
been  taken  as  the  unit.  This  reduces  it  all  to  a  common  standard, 
so  that  the  traffic  in  one  city  can  be  easily  compared  with  that  of 
another. 

In  1885  a  series  of  observations  were  made  under  the  direction 
of  Gen.  F.  V.  Greene  to  determine  the  amount  of  traffic  in  several 
American  cities.  The  figures  represent  the  number  of  vehicles  of 
all  kinds  passing  between  7  A.M.  and  7  P.M. 

Broadway,  New  York 7,811 

Broad  Street,  Philadelphia 6,081 

Devonshire  Street,  Boston 5,362 

Douglass  Street,  Omaha 4,752 

Fifteenth  Street,  opp.  Treasury,  Washington 4,520 

Clark  Street,  Chicago 4,389 

For  comparison  the  number  of  vehicles  passing  in  twenty-four 
hours  in  some  foreign  cities  are  given: 

PABIS. 

Rue  de  Rivoli 42,035 

Avenue  de  1'Opera 29,500 

Rue  Croix  des  Petit  Champs 20,480 

Rue'St.  Honore 19,672 

LONDON. 

King  William  Street 26,793 

Gracechurch  Street 15,585 

Queen  Victoria  Street 16,531 

Cheapside   15,206 

SYDNEY,   AUSTRALIA. 

George  Street 11,960 

Width  of  Roadway. — The  distance  between  curbs  affects  traffic 
as  it  tends  to  scatter  or  congest  it.  The  wider  a  pavement  is  the 
more  even  will  be  its  wear.  If  several  lines  of  travel  can  be  main- 
tained irregularly,  the  wear  on  the  surface  will  be  more  uniform 
and  a  better  service  received  from  the  pavement.  When  vehicles 
are  restricted  to  direct  lines  of  travel,  the  wheels  move  in  prac- 


THE  THEORY  OF  PAVEMENTS.  149 

tically  the  same  place  from  day  to  day,  and  the  result  is  a  rough 
and  uneven  surface  in  a  comparatively  short  space  of  time. 

Character  of  Pavement. — By  this  is  meant  the  detailed  method 
by  which  any  particular  material  is  laid.  Asphalt  pavements  have 
been  standardized,  slight  variations  sometimes  being  made  to  meet 
special  traffic  conditions.  But  with  stone,  brick,  and  wood  it  is 
very  different.  Foundations  vary  for  all,  and  the  joint  filling  of 
each  is  what  the  experience  or  inclination  of  the  particular  engineer 
may  suggest.  Wood  of  one  variety  is  used  in  one  locality,  and  a 
different  kind  in  another.  It  is  treated  chemically  in  one  city,  and 
laid  in  its  natural  condition  in  others,  so  that  the  word  "  wood  " 
alone  means  very  little  as  to  the  exact  character  of  the  pavement. 

Presence  or  Absence  of  a  Street-car  Track. — A  car-track  has  a 
great  bearing  on  the  action  of  traffic.  On  a  rough,  poorly  paved 
street  where  the  cars  run  at  long  intervals,  vehicles  naturally  make 
use  of  the  track,  thus  relieving  the  pavement  from  a  large  amount 
of  its  natural  wear.  On  the  other  hand,  on  a  well-paved  street 
where  cars  run  frequently,  the  traffic  is  confined  to  the  space  be- 
tween the  tracks  and  the  curb,  with  all  the  evils  of  restricted  travel. 
The  appreciation  contractors  have  of  this  is  shown  by  the  fact  that 
in  1897  bids  for  asphalt  pavement  in  Brooklyn,  X.  Y.,  averaged 
$0.98  per  square  yard  on  sixty-eight  streets  free  from  tracks, 
and  $1.26  on  eleven  streets  where  there  were  tracks. 

State  of  Repair. — This  is  of  vital  importance  to  a  street  pave- 
ment. If  holes,  depressions,  ruts,  or  any  defect  in  the  surface  are 
allowed  to  remain  for  any  length  of  time,  the  material  is  displaced 
and  consequently  is  worn  abnormally.  This  fact  is  not  fully  ap- 
preciated by  most  city  officials,  but  should  they  watch  the  effect 
of  travel  upon  granite  blocks  loosely  paved  in  a  trench,  they  would 
soon  be  convinced.  This  is  especially  true  of  such  materials  as 
asphalt  or  broken  stone. 

Cleanliness. — The  effect  of  street  refuse  on  a  pavement  varies 
with  its  character.  An  imperishable  material  is  benefited  by  hav- 
ing a  cushion  of  detritu's  upon  it.  It  serves  as  a  carpet  to  protect 
the  pavement,  which  when  the  cushion  is  heavy  enough  becomes 
the  foundation  only.  This  fact  will  often  explain  why  certain 
materials  are  seemingly  so  much  more  durable  in  a  small  city  than 
in  a  large  one.  A  poor  brick  pavement,  for  instance,  will  often  give 


150        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

good  results  in  a  small  place  where  the  pavements  are  cleaned  only 
at  long  intervals,  when  it  would  rapidly  fail  if  kept  clean  under  the 
same  traffic. 

This  will  not  hold  good,  however,  with  wood  or  asphalt  streets. 
Any  street  debris  collects  and  retains  moisture  which  hastens  the 
action  of  disintegration  and  decay  in  any  perishable  material. 

At  one  of  the  meetings  of  the  National  Brick  Manufacturers' 
Association  one  member  asked  if  city  streets  were  not  kept  too 
clean;  if  brick  pavements  would  not  last  longer  and  be  less  noisy 
if  they  were  allowed  to  become  more  dirty.  Although  answered  in 
the  affirmative,  he  was  told  that  in  these  times  city  streets  would 
be  kept  clean  despite  the  effect  upon  the  material  of  the  pave- 
ment. 

r.  All  of  the  above  conditions  modify  the  action  of  traffic  and  thus 
affect  the  durability  of  any  material.  This  property  of  durability 
has  been  considered  tq  have  a  value  of  21. 

EASINESS  or  CLEANING. — The  experience  of  New  York,  Wash- 
ington, Buffalo,  and  other  large  cities  in  cleaning  streets  has  de- 
monstrated to  citizens  and  taxpayers  that  it  is  not  only  feasible 
but  very  desirable  to  have  pavements  kept  free  from  natural  street 
detritus.  It  has  been  shown  so  conclusively  that  it  is  an  accepted 
fact  that  it  is  not  alone  desirable,  but  that  it  is  absolutely  neces- 
sary. The  expense  of  street-cleaning  is  very  great,  and  any  device 
or  any  street-construction  that  will  reduce  it  will  be  gladly  wel- 
comed by  city  officials. 

The  appropriation  for  the  Street  Cleaning  Department  of  New 
York  City  for  1900  was  $5,031,282.  The  benefit  of  smooth  pave- 
ments to  this  department  will  be  appreciated  from  a  statement  made 
in  1896  by  Col.  Geo.  -E.  Waring,'  Jr.,  then  Street  Cleaning  Com- 
missioner of  New  York  City.  At  a  meeting  of  the  American  So- 
ciety of  Civil  Engineers  he  said  that  if  all  the  streets  of  New  York 
were  paved  with  asphalt  where  the  grades  would  permit,  and  the 
street-car  tracks  constructed  with  grooved  rails,  the  cost  of  sweep- 
ing the  entire  city  would  be  reduced  from  $1,200,000  per  annum 
to  $700,000.  That  is,  there  would  be  a  saving  annually  of  $500,000, 
which  capitalized  at  4  per  cent  would  amount  to  $12,500,000  in 
a  city  that  then  had  a  pavement  mileage  of  431  miles,  of  which 


THE  THEORY  OF  PAVEMENTS.  151 

94  were  paved  with  asphalt.  A  value  of  15  is  given  to  easiness  of 
cleaning. 

RESISTANCE  TO  TRAFFIC. — This  is  an  important  item.  One  of 
the  chief  provinces  of  a  pavement  is  to  reduce  this,  and  conse- 
quently any  pavement  that  can  bring  it  to  a  minimum  is  of  special 
value.  A  mechanical  device  that  would  reduce  the  friction  of  a 
machine  25  or  50  per  cent  would  be  recognized  at  once  as  of  great 
benefit.  There  is  fully  this  difference  in  the  various  pavements,  and 
this  must  be  recognized  and  considered  before  deciding  on  any 
particular  material.  If  one  horse  can  draw  on  one  pavement  a  load 
that  would  require  two  horses  on  another,  the  truckman  at  once 
sees  the  importance  of  a  proper  selection.  Light  resistance  to 
traffic  is  valued  at  15. 

NON-SLIPPERINESS. — The  slipperiness  of  a  pavement  depends 
upon  its  material  and  also  upon  its  condition.  The  efficiency  of  a 
draft-horse  varies  with  his  foothold.  If  that  be  good,  he  can  use 
his  entire  strength  to  draw  his  load;  while  if  he  be  in  constant 
danger  of  slipping  and  falling,  he  will  accomplish  very  little.  In- 
stead of  using  all  his  power  to  overcome  the  resistance  of  the  load, 
he  uses  it  only  to  the  slipping-point. 

The  condition  of  the  weather  and  the  climate  modify  this.  An 
illustration  of  this  is  shown  in  a  case  where  observations  were  being 
taken  on  several  asphalt-paved  streets  in  extreme  winter  weather. 
On  the  first  day  the  hourly  traffic  was  225  tons  between  11  and  12 
o'clock,  reaching  270  tons  between  3  and  4  o'clock  P.M.  On  the 
following  day  the  traffic  between  11  and  12  o'clock  was  305  tons. 
About  2  o'clock  snow  began  to  fall,  the  mercury  being  about  zero, 
making  the  pavement  so  slippery  that  the  traffic  was  reduced  to  40 
tons  between  3  and  4  o'clock,  and  the  street  was  soon  practically 
deserted.  The  same  results  were  obtained  on  all  other  streets 
where  observations  were  being  taken.  Non-slipperiness  is  assigned 
a  value  of  7. 

In  the  light  of  the  above  this  value  may  seem  small,  but  it  must 
"be  remembered  that  these  special  conditions  seldom  arise,  an$,  while 
effective  while  they  do  exist,  do  not  have  as  much  influence  as  a 
smaller  force  acting  continually. 

EASE  OF  MAINTENANCE. — Maintenance  is  closely  allied  to  first 
cost,  and  many  engineers  think  that  they  should  be  considered 


152        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

together.  To  a  certain  extent  this  is  true,  but  mainly  when  the 
question  of  ultimate  economy  is  being  considered.  The  cost  of  re- 
pairs liable  to  be  incurred  to  keep  a  pavement  in  good  condition 
should  be  ascertained  as  accurately  as  possible  in  advance.  No 
material  can  be  intelligently  adopted  without  it.  What  often 
seems  a  wise  and  sound  selection  is  ruled  out  simply  by  the  cost  of 
repairs.  All  works  constructed  by  man  require  constant  attention, 
and  a  pavement  is  no  exception  to  the  general  rule.  But  that 
material  which  needs  the  least  and  allows  that  to  be  done  at  the 
least  expense,  as  well  as  inconvenience  to  the  public,  is  the  best, 
other  things  being  equal.  This  property  has  been  ranked  at  10. 

FAVOKABLENESS  TO  TRAVEL. — By  this  is  meant  the  ease  and 
comfort  that  are  enjoyed  in  driving  over  a  smooth  pavement,  and 
also  the  decrease  in  the  wear  and  tear  of  vehicles,  as  compared 
with  one  that  is  rough  and  uneven.  It  is  difficult  to  estimate  this 
exactly,  but  some  approximations  have  been  made. 

The  French  engineers  say  that  50  per  cent  is  saved  in  the  wear 
and  tear  by  having  smooth  pavements. 

A  London  engineer  in  1827  stated  that  good  pavements  in  Lon- 
don, Westminster,  and  Southwark  would  save  £140,000  per  annum 
in  wear  and  tear  of  vehicles  and  horses.  The  area  included  in  the 
above  was  3818  acres,  but  it  must  be  remembered  that  the  streets  of 
London  at  that  time  were  in  a  specially  bad  condition. 

In  a  paper  read  before  the  Institution  of  Civil  Engineers  in 
1871  Mr.  Geo.  F.  Deacon  said:  "  Since  the  new  Liverpool  pave- 
ments have  been  constructed  without  giving  credit  for  the  great 
reduction  of  wear  and  tear  of  horses  and  vehicles,  there  was  a  sav- 
ing of  £10,000  per  year  for  every  mile  of  the  new  pavements-  now 
laid  on  the  dock  line  of  the  streets  of  Liverpool." 

Smooth  pavements  are  a  luxury  also.  It  is  a  pleasure  to  drive 
on  some  streets,  and  positively  painful  on  others.  Wheeled  vehicles 
are  equipped  with  pneumatic  tires  to  make  the  pleasure  as  great  as 
possible,  but  much  can  be  done  to  aid  it  in  the  pavements  itself. 
With  the  introduction  of  the  automobile,  and  the  possibilities  of 
its  extension,  this  property  of  favorableness  to  travel  is  bound  to 
receive  more  attention  from  year  to  year.  At  the  present  time  it 
is  valued  at  5. 

SANITAEINESS. — Another  important  requisite  of  a  pavement  is 


THE  THEORY  OF  PAVEMENTS.  153 

that  it  should  be  sanitary.  A  great  amount  of  decaying  organic 
matter,  house-garbage,  horse-droppings,  and  various  kinds  of  filth 
must  be  deposited  in  the  streets  despite  the  utmost  care  of  citizens 
and  public  officials.  Any  pavement  that  will  allow  any  of  this  to- 
collect  in  joints,  or  soak  down  to  the  surface  to  the  underlying 
soil,  out  of  the  reach  of  street-cleaners,  must  be  deleterious  to  the 
public  health.  Any  material  that  will  readily  absorb  moisture  and 
give  it  forth  in  dry  seasons  must  be  considered  as  unsanitary. 
Therefore  a  pavement  that  has  a  smooth  surface,  is  impervious  to 
water,  and  is  not  made  up  of  organic  matter  subject  to  decay  will 
be  desirable  from  the  standpoint  of  the  sanitarian. 

Noise,  too,  is  an  important  factor.  A  noisy  material  prevents 
sleep,  rasps  on  the  nerves  of  both  the  sick  and  the  well,  and  prevents 
conversation  on  the  street.  This  is  considered  of  so  great  im- 
portance in  large  cities  that  in  apportioning  the  funds  allowed  for 
repaving  New  York  City  special  consideration  is  given  to,  and  a 
separate  sum  set  aside  for,  smooth  pavements  around  schools, 
churches,  and  hospitals.  Sanitariness  is  rated  at  13. 

Having  now  studied  somewhat  in  detail  the  characteristics  of  a 
pavement  and  obtained  a  value  for  each,  it  will  be  in  order  to  take 
up  the  different  paving  materials  themselves,  and  by  careful  ex- 
amination determine  how  much  of  each  total  is  to  be  apportioned 
to  each  according  as  it  approaches  perfection  in  each  property. 

The  pavements  that  will  be  considered  are:  oblong  granite- 
blocks  laid  on  six  inches  of  cement  concrete  with  tar  and  gravel 
joints  called  granite  A;  granite  blocks  laid  on  a  sand  base  with  sand 
joints,  called  granite  B;  sheet  asphalt,  wearing  surface  two  inches 
thick  and  binder  one  inch,  on  six  inches  of  concrete;  vitrified  brick,, 
also  laid  on  a  six-inch  concrete  base  with  joints  filled  with  pitch  or 
Portland  cement;  Belgian  trap-rocks  on  sand;  macadam  eight 
inches  thick;  and  cobblestone.  Wood  is  not  taken  into  considera- 
tion because  it  is  at  present  being  laid  in  but  a  few  Western  cities,, 
and  untreated  cannot  be  considered  as  a  paving  material.  It  has 
also  been  laid  in  so  many  different  ways  and  of  so  many  varieties 
that  each  case  would  require  discussion  by  itself. 

It  may  be  said  that  cobblestone  is  a  material  of  the  past.  This 
is  undoubtedly  true,  but  its  use  illustrates  the  scope  of  the  table. 


154        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

First  Cost. — This  of  course  will  vary  in  every  locality,  and  a 
different  apportionment  must  be  made  for  every  change  in  price. 
The  following  figures  are  based, upon  the  average  prices  bid  in 
Brooklyn,  N.  Y.,  in  1897  (all  per  square  yard  complete): 

Granite   A $2.50 

Granite  B 1.65 

Asphalt 1.75 

Brick  2.00 

Belgian   1.40 

Macadam   0.75 

Cobblestone   0.40 

Assuming  their  values  to  be  inversely  as  their  cost,  granite  A 
has  2,  granite  B  4,  asphalt  4,  brick  3,  Belgian  5,  macadam  7,  and 
cobble  14. 

Durability. — This,  as  ;has  already  been  seen,  varies  greatly  ac- 
cording to  many  conditions,  so  that  any  conclusion  must  be  gen- 
eral. 

It  must  be  remembered,  also,  that  there  are  two  ends  to  all 
pavements,  a  physical  and  an  economical  end.  The  former  comes 
when  the  material  is  so  worn  out  that  it  cannot  be  repaired  and 
must  be  relaid;  the  latter  when  the  cost  of  repairs  is  so  great  that 
it  will  be  economy  in  the  end  to  relay  at  once.  The  former  test  will 
generally  be  applied  to  stone,  brick,  or  any  block  pavement,  and 
the  latter  to  asphalt  or  macadam.  When  a  pavement  is  made  of 
moderately  sized  parts  of  practically  the  same  character,  the  wear 
on  the  parts  is  about  the  same  amount,  and  to  repair  it  requires 
taking  up  the  old  material  and  replacing  it  with  new  rather  than 
adding  to  the  material  on  the  street.  But  when  a  pavement  is 
made  up  of  parts  so  small  that  they  must  be  consolidated  into  a  con- 
tinuous whole  it  is  different. 

The  physical  end  of  a  pavement  can  be  determined  by  observa- 
tion as  the  blocks  wear  out. 

Asphalt  and  macadam  wear  away  by  degrees,  and  can  be  added 
to  in  whatever  quantity  it  may  be  desired  and  its  physical  life  thus 
prolonged  indefinitely.  The  economic  test  must  then  be  applied 
.to  ascertain  when  the  repairs  must  be  stopped  and  a  new  pavement 
laid.  Assume  a  street  to  be  paved,  and  the  expense  of  keeping  it  in 


THE  THEORY  OF  PAVEMENTS.  *     155 

repair  is  so  great  that  the  question  arises,  shall  it  be  repaved  or  the 
repairs  continued? 

Let  N  =  life  of  proposed  pavement; 
C  =  cost  per  square  yard; 
I  =  rate  of  interest; 

R  =  estimated  cost  if  distributed  over  entire  life; 
A  =  sinking  fund  to  be  paid  each  year  to  equal  C  at  end  of 

AT  years. 
r> 

Then  A  +  CI  +  T-  =  annual  expense  of  new  pavement. 

Take,  for  instance,  an  asphalt  pavement,  and  let  N  =  15  years, 
C  =  1.50,  /  =  3J,  and  R  =  0.40.  Then  A  will  equal  .0807  and  the 
equation  becomes  $0.0807  +  .0525  +  .0267  =  $0.1599;  or  if  the 
street  be  repaved,  it  will  cost  annually  $0.16  till  it  is  renewed.  Con- 
sequently if  the  life  of  asphalt  be  correctly  assumed  at  15  years, 
it  should  not  be  repaved  until  the  annual  cost  approaches  $0.16 
per  square  yard.  Assuming  the  life  to  be  20  instead  of  15  years 
and  applying  the  formula  as  before,  the  annual  cost  will  be  reduced 
to  $0.1356  per  yard. 

The  author  believes  that  this  is  the  scientific,  the  engineering, 
and  the  only  true  way  of  telling  when  an  asphalt  pavement  should 
be  relaid.  The  only  element  to  modify  this  principle  is  the  incon- 
venience traffic  and  property  owners  on  the  street  are  put  to  while 
repairs  are  being  made.  The  determination  of  this  must  be  made 
in  each  case.  But  the  principle  of  the  formula  is  correct,  and  when 
cities  have  had  a  larger  experience  with  asphalt  pavements,  and 
repair  accounts  are  kept  in  a  more  intelligent  way,  there  will  be,  no- 
difficulty  in  determining  the  variables. 

A  series  of  experiments  were  made  in  St.  Louis  in  1880  to  deter- 
mine the  resistance  to  abrasion  of  several  kinds  of  paving  material. 

Strips  of  pavement  22  inches  wide  were  laid  of  fire-brick, 
asphalt  blocks,  granite  and  limestone  blocks.  A  traffic  standard  of 
50  tons  per  day  per  foot  of  width  of  roadway  was  adopted,  and 
a  two-wheeled  cart  with  2^-inch  tires  loaded  800  Ibs.  per  inch  was 
rolled  over  the  different  strips  long  enough  to  equal  a  traffic  of 
8J  years.  The  fire-brick  lost  9  per  cent  in  weight  and  a  depth  of 
-J  inch,  with  about  one-half  broken.  Asphalt  blocks  lost  14  per 


156        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


cent,  limestone  blocks  10  per  cent,  while  the  wear  on  the  granite 
was  hardly  appreciable. 

The  officials  of  different  European  cities  give  the  average  life 
of  the  different  materials  as  follows: 

TABLE  No.  45. 


Granite. 

Asphalt,  Years. 

Wood. 

Olassrow                       . 

50 

6 

30 

12  to  15  j 

Redwood  8 

Liverpool  ...                  .  .  .  . 

30 

12 

Australian  15 
15  to  18 

\ 

5  to  8  for  Baltic  deal 

30 

.......f 

Australian  12 

8 

From  the  above  and  data  collected  from  American  cities  the 
estimated  life  of  granite  A  is  25  years,  granite  B  20  years,  brick  15 
years,  wood  10  to  15  years,  asphalt  18  years,  Belgian  20  years, 
macadam  8  years,  and  cobble  18  years. 

These  estimates  give  to  granite  A  a  value  of  21,  granite  B  17, 
"brick  13,  asphalt  15,  Belgian  17,  macadam  7,  and  cobble  15. 

Easiness  of  Cleaning. — Some  figures  have  already  been  given 
showing  the  benefits  of  smooth  pavements  when  they  are  to  be 
cleaned.  How  necessary  this  is  can  be  recognized  from  a  state- 
ment made  by  a  committee  of  the  Society  of  Arts,  London,  in  1875, 
to  the  effect  that  at  that  time  it  was  estimated  that  1000  tons  of 
"horse-manure  was  being  dropped  daily  upon  the  streets  of  Lon- 
don. This  had  to  be  taken  up  and  removed  to  avoid  being  incor- 
porated into  the  human  system  through  the  respiratory  organs. 
Other  refuse  of  all  kinds  collects  upon  our  streets,  and  the  pave- 
ment that  uniformly  presents  a  hard,  smooth,  and  even  pavement 
is  cleaned  at  much  less  expense  than  one  that  is  rough  and  uneven. 
In  accordance  with  this  principle,  then,  granite  A  has  a  value  of 
11,  granite  B  8,  asphalt  15,  brick  12,  Belgian  7,  macadam  5,  and 
cobble  2. 

Light  Resistance  to  Traffic. — Many  experiments  have  been  made 
to  determine  the  force  necessary  to  draw  a  given  lo'ad  over  roads  and 
pavements  of  different  character.  The  most  of  them  were  made, 
however,  a  good  many  years  ago,  those  of  Morin  having  been  carried 


THE  THEORY  OF  PAVEMENTS.  157 

out  in  1843,  and  those  of  Macneil  in  1838.  Since  that  time  changes 
have  occurred  in  the  same  kind  of  pavement,  one  of  stone  block, 
for  instance,  being  very  different  from  that  of  fifty  years  ago,  so 
that  the  results  arrived  at  then  may  not  be  absolutely  correct  to- 
day, but  relatively  they  should  not  be  far  from  right.  Then,  too, 
the  actual  condition  of  the  pavement  must  vary  results  consider- 
ably. Differences  of  temperature  would  change  results  on  asphalt, 
the  traction  being  appreciably  greater  in  the  summer,  when  the 
pavement  is  soft,  than  in  the  winter.  It  is  to  be  regretted  that  more 
modern  experiments  have  not  been,  undertaken  on  any  extended 
scale  with  modern  appliances  to  settle  this  question. 

At  the  Atlanta  Exposition  in  1895  the  Department  of  Agricul- 
ture experimented  to  some  extent  with  some  roads  and  pavements 
that  were  available  at  that  time  and  place.  Table  No.  46  gives  the 
^esults  reached. 

TABLE  No.  46. 

Pounds. 

Loose  sand  (experimental) 320 

Best  gravel,  park  road 51 

Best  clay 98 

Best  macadam 38 

Poor  block  pavement 42 

Cobblestone 54 

Poor  asphalt 26 

Table  No.  47  gives  the  force  in  pounds  per  ton  required  to 
draw  a  load  over  different  surfaces  as  given  by  Prof.  Haupt  in  a 
paper  published  in  Journal  of  the  Franklin  Institute  in  December, 
1889. 

In  1893  the  Studebaker  Brothers  of  South  Bend,  Ind.,  made 
some  experiments  on  this  subject,  and  a  portion  of  their  results 
is  given  in  Table  No.  48.  The  figures  represent  force  in  pounds 
per  ton. 

These  results  would  seem  to  indicate  that  a  load  is  not  hauled 
much  more  easily  on  wide  tires  over  ordinary  roads  than  on  narrow, 
and  that  on  stone  pavements  the  narrow  tires  actually  require  less 
traction.  This  last  is  probably  due  from  the  fact  that  a  stone 
pavement  must  necessarily  be  more  or  less  rough,  and  that  a  wide 
tire  will  be  apt  to  pass  over  more  bunches  than  a  narrow  one,  and 
as  the  load  must  be  simply  lifted  over  the  bunch  in  either  case, 


158        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

TABLE  No.  47. 
Character  of  Roadway.  Pounds  per  Ton. 

Sand  400 

Gravel 200 

Ordinary  earth 200 

Dry  clay 100  to  66 

Good   cobble 133  to  66 

Ordinary  cobble 250 

Ordinary  macadam 80  to  57 

French  macadam 40 

Stone  block 80 

Belgian  block 50 

Belgian  block,  well  laid 33 

Asphalt ' 15 

Smooth  granite  trams 12 

Iron  trams 10 

TABLE  No.  48. 

Diameter  of  wheels  3  ft.  8  in.  and  4  ft.  6  in. 

4-inch  Tire.  IJ^-inch  Tire. 

To  Start.       To  Move.  To  Start.      To  Move. 

Block  pavement 161              46  142              35 

Good  sand  roads 323            127  343            180 

Good  gravel  roads 276              81  308              83 

Muddy  roads 369            254  422            237 

more  traction  will  be  required  with  wide  tires  on  a  hard  surface 
that  is  not  smooth. 

The  committee  of  the  Society  of  Arts  previously  referred  to  ex- 
perimented on  the  streets  of  London  in  1875  to  ascertain  the  force 
required  to  draw  loads  over  different  roadways  at  varying  rates  of 
speed.  Table  No.  49  gives  results. 

The  report  added  that  the  asphalt  experimented  on  was  not 
in  good  condition,  and  for  that  reason  the  force  shown  for  asphalt 
was  undoubtedly  higher  than  it  otherwise  would  have  been.  These 
figures,  however,  are  valuable  as  they  give  the  effect  caused  on  the 
draft  of  increased  speed. 

Table  No.  50  is  made  up  from  the  results  of  different  experi- 
menters, the  figures  representing  the  force  in  pounds  to  draw  one 
ton  at  a  speed  of  approximately  3  miles  per  hour. 

From  all  these  figures  it  is  estimated,  taking  into  considera- 
tion the  varying  conditions  under  which  all  tests  were  made,  as  well 
as  the  improved  character  of  pavements  at  present,  that  the  force 


THE  THEORY  OF  PAVEMENTS. 


159 


TABLE  No.  49. 

r«.    .         f.  ,>„„,  Speed  in  Miles       Force  in  Pounds 

Character  of  Pavement.  *Jer  Hom.  to  move  Qne  Ton< 

Gravelly  macadam 6.945  44 

Do 3.45  39.8 

Granite  macadam  side  of  tramway  -j 

Do 2.557  10.5 

Granite  blocks  by  freshly  laid  . .  \  4'239 

(  2.775  84.4 

Asphalt  5.025  30.8 

Do 3.56  24.2 

Do 5.687  29.3 

Wood  3.932  41.1 

Do 3.278  35.6 

Do 3.827  34.8 

Good  macadam 6.65  37.9 

TABLE  No.  50. 

Character  of  Roadway.  Pounds.                     Authority. 

Ordinary  dirt  road 200  Bevan 

Hard  gravel 66|  Bevan 

"     66|  Minard. 

"      51  U.  S.  Qovt. 

Bad  macadam 143  Gordon 

Old  macadam 100  Navier 

Good  macadam,  wet 86  to  66f  Morin 

Best  macadam 33i  to  43£  Gordon 

28|to46i  Morin 

44f  Rumford 

38  U.  S.  Govt. 

Ordinary  cobblestone 125  Kossack 

Good  cobblestone 62^  Kossack 

Cobblestone 54  U.  S.  Govt. 

Belgian  block 47£  Navier 

"    23to44$  Morin 

" 31  U.S.  Govt. 

"      good 33£  Rumford 

Ordinary  stone  block 80  Minard 

"     33 

Good  stone  block 40  Rumford 

London  stone  block 33  Gordon 

Poor  stone  block 42  U.  S.  Govt 

Asphalt...* 15  Gordon 

"     poor 26  U.  S.  Govt. 

"      15  Haupt 

"      24  London  Experiment 


160        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

expressed  in'  pounds  to  draw  one  ton  over  the  different  pavements 
herein  considered  would  be:  granite  A  34,  granite  B  40,  asphalt  16, 
brick  20,  Belgian  40,  macadam  40,  and  cobblestone  65.  Tliis  will 
give  a  percentage  to  granite  A  of  7,  granite  B  6,  asphalt  15,  brick 
12,  Belgian  6,  macadam  6,  and  cobble  4. 

The  general  opinion  among  engineers  is  that  the  tractive  force 
varies  inversely  as  the  diameter  of  the  wheels,  but  some  say  in- 
versely as  the  square  root  of  the  diameter.  Mr.  W.  Hewitt  in  a 
paper  before  the  Surveyors'  Institution  of  England  says:  "From 
experiments  made  with  Eastren  and  Anderson's  horse-dynamom- 
eter at  the  Royal  Agricultural  Show,  1874,  a  slightly  greater  ratio 
than  inversely  as  the  diameter  was  given,  and  I  am  inclined  to  think 
that  inversely  as  the  diameter  is  the  more  correct  View  of  the  two." 

Slipperiness. — A  great  many  conditions  affect  this  property: 
conditions  of  the  street,  temperature,  whether  wet,  damp,  or  dry, 
etc. 

Mr.  Wm.  Haywood,  Engineer  to  the  Sewer  Commissions  of  Lon- 
don, made  some  very  extended  observations  in  the  London  streets 
in  1873  to  determine  the  liability  of  horses  slipping  on  asphalt, 
granite,  and  wood  pavements. 

The  asphalt  observed  was  the  ordinary  rock  asphalt  of  that 
time,  2J  inches  thick  on  a  9-inch  concrete  base,  with  the  surface  in 
good  condition.  The  grades  varied  from  1  in  58  to  1  in  550. 

The  granite  pavement  consisted  of  Aberdeen  blocks  3  inches 
wide,  9  inches  deep,  and  from  9  to  15  inches  long,  laid  stone  to 
stone,  the  joints  being  filled  with  stone-lime  grout.  The  pavement 
as  a  whole  was  not  in  good  condition.  The  grade  varied  from  1  in 
30  to  1  in  1000. 

Two  wood  pavements  were  experimented  with.  One  was  formed 
of  fir  blocks  3  inches  wide,  5  inches  deep,  and  9  inches  long.  The 
blocks  were  laid  touching  each  other  at  the  ends,  but  crosswise  of 
the  street;  the  joints  were  f  inch  wide,  filled  in  with  thin  gravel 
and  grouted  in  with  a  bituminous  composition.  The  other  con- 
sisted of  beech  blocks  3^  inches  wide,  4J  inches  deep,  and  6  inches 
long,  with  J-inch  joints  at  side  and  ends,  filled  in  with  cement 
grout.  The  grades  varied  from  1  in  30  to  1  in  260. 

The  asphalt  T?as  sprinkled  slightly  with  sand,  and  the  wood 
four  times  with  gravel.  The  wood  and  granite  were  watered  to  lay 


TEE  THEORY  OF  PAVEMENTS. 


161 


the  dust,  but  the  asphalt  was  not  treated.  All  the  pavements  were 
kept  as  clean  as  their  nature  and  respective  surfaces  admitted  with 
the  usual  amount  of  labor.  All  observations  were  taken  between 
8  A.M.  and  9  P.M. 

The  mean  number  of  horses  passing  daily  in  March  and  April 


Ashpalt. 


Granite. 


Wood, 


(  Cheapside  12,366 
(  Poultry  10,920 

j  King  William  Street  8,555 
\  Cannon  Street  5,350 

(  King  William  Street  21,162 

*  (  Gracechurch  Street  11,484 

Table  No.  51  shows  the  total  number  of  horses  that  fell  on  the 
different  streets  during  the  fifty  days  on  which  observations  were 
taken,  as  well  as  the  daily  <mean. 

TABLE  No.  51. 


Character  of 
Pavement. 

Street. 

Distance 
Travelled 
in  Miles. 

Total 
Number 
of 
Accidents 

Miles 
Travelled 
for  Each 
Accident. 

Daily 
Mean. 

Asphalt  .  .               \ 

Cheapside 

172,783 

932 

185 

18.64 

Granite  j 
Fir-  wood  •< 

Poultry 
King  William  Street 
Cannon  Street 
King  William  Street 

31,022 
54,683 
40,884 

169  69C 

134 
429 
290 

380 

231 
127 
140 

446 

2.86 

8.58 
5.80 

7  60 

Gracechurch  Street 
Gracechurch  Street 

9  461 

162 

58 

3  24 

478  523 

2327 

-  46  72 

The  mean  being:  Asphalt  191  miles  travelled  for  each  accident. 
Granite  132      "  "      " 

Wood     330      "  "         "       " 

"Accidents"  in  this  connection  mean  falls  on  knees,  falls  on 
haunches,  and  complete  falls.  No  account  was  taken  of  horses 
slipping  simply.  During  the  last  thirty-two  days  record  of  these 
different  occurrences  was  kept,  and  the  percentage  of  each  is  shown 
in  Table  No.  52. 

TABLE  No.  52. 

On  Knees.  On  Haunches.  Complete.    ' 

Asphalt 32.04  24.48  43.48 

Granite  40.39  7.56  46.05 

Wood  .  84.97  3.07  11.96 


162        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Table  No.  53  shows  the  distance  in  miles  horses  travelled  with- 
out accident  under  three  different  conditions  of  surface  moisture. 

TABLE  No.  53. 

Pavement.  Dry.  Damp.  Wet. 

Granite 78  168  537 

Asphalt 223  125  192 

Wood   646  193  432 

Mr.  Haywood  thinks  that  the  accidents  on  the  beech  pavements 
should  be  eliminated,  as  they  were  not  typical  pavements,  when  the 
true  order  of  slipperiness  would  be: 

Miles. 

Granite 132 

Asphalt 191 

Wood   446 

It  must  be  borne  in  mind  that  the  asphalt  experimented  on  was 
the  European  natural  rock  asphalt,  which  is  admittedly  much  more 
slippery  than  American  asphalt. 

In  summing  up  Mr.  Haywood  says: 

"  Taking  the  whole  group  of  conditions  into  account,  the 
asphalt  was  the  most  advantageously  placed,  the  wood  was  the  next 
so,  and  the  granite  was  the  worst  placed. 

On  the  average  of  the  whole  fifty  days'  observations,  the  granite 
was  found  to  be  the  most  slippery,  the  asphalt  'the  next  so,  and  the 
wood  the  least. 

Separating  the  accidents  under  three  conditions  of  surface  as 
regards  moisture,  it  appears  that  asphalt  was  most  slippery  when 
merely  damp,  and  safest  when  dry;  that  granite  was  most  slippery 
when  dry,  and  safest  when  wet;  that  wood  was  most  slippery  when 
-damp,  and  safest  when  dry." 

In  1885  Capt.  F.  V.  Greene  had  a  series  of  observations  made 
in  ten  of  the  principal  cities  of  the  United  States  to  determine  the 
relative  slipperiness  of  the  same  kinds  of  pavements  as  laid  in  this 
country.  From  his  results  he  decided,  that  on  pavements  in  Ameri- 
can cities  a  horse  would  travel  272  miles  on  wood,  413  on  granite, 
and  583  on  asphalt  without  an  accident.  His  accidents  were 
divided  also  into  falls  upon  the  knees,  falls  upon  the  haunches, 
and  complete  falls.  On  a  rough  pavement  falls  upon  the  knees 
should  not  be  wholly  charged  to  slipperiness,  as  a  great  many  must 


THE  THEORY  OF  PAVEMENTS.  163 

be  caused  by  stumbling.  Capt.  Greene  found  that,  of  a  total  of  84 
'falls/  68  were  upon  the  knees.  Assuming  that  one-half  of  the 
latter  were  stumbles  only,  the  deduction  would  be  that  a  horse 
would  travel  698  miles  on  granite  without  an  accident  due  to  slip- 
periness.  These  results  of  course  are  general. 

From  these  and  other  observations,  granite  A  is  given  a  value 
of  6,  granite  B  5,  asphalt  3,  brick  6,  Belgian  3,  macadam  7,  and 
cobble  5. 

Maintenance. — The  cost  of  repairs  to  pavements  varies  greatly 
in  different  cities.  It  is  governed  principally  by  the  character  of 
the  material,  nature  and  amount  of  traffic,  and  the  condition  in 
which  the  streets  are  kept.  No  satisfactory  records  are  available 
on  this  subject.  Few  cities  keep  their  accounts  in  such  a  manner 
that  it  is  possible  to  tell  how  much  money  has  been  spent  on  dif- 
ferent kinds  of  pavements.  Then,  too,  officials  have  different  stand- 
ards of  good  repair.  One  city  will  not  tolerate  what  is  considered 
very  good  in  another.  Granite  when  properly  laid  requires  but 
little  attention  for  some  years,  and  then  by  relaying  the  blocks  the 
pavement  may  be  made  good  for  a  number  of  years. 

The  Surveyor  of  the  Greenwich,  Eng.,  District  Board  of  Works 
said  in  1891  that  a  granite-cube  paved  road  cost  12  cents  per  yard 
per  annum  for  repairs. 

In  Birmingham,  Eng.,  granite  lasts  seven  years  without  any 
cost,  for  the  next  seven  years  from  6  to  14  cents  per  yard  per  year, 
after  which  in  the  heaviest-traffic  streets  it  would  require  relaying 
at  a  cost  of  about  73  cents  per  yard,  when  it  would  last  as  above 
another  fourteen  years,  and  even  then  the  best  of  the  stone  could 
be  redressed  and  used  on  light-traffic  streets,  and  the  remainder 
used  for  macadam.  Wood  costs  nothing  for  the  first  year,  then 
from  15  to  18  cents  per  yard  per  year  for  twenty  years  after,  ac- 
cording to  location. 

In  Dresden  macadam  cost  for  repairs  in  1889  4£  cents  per  yard. 

In  London  in  1884  macadam  cost  on  Parliament  Street  70  cents, 
on  Whitehall  Street  71  cents,  and  on  Victoria  Street  50  cents  per 
yard  for  repairs.  On  five  principal  London  streets  granite  averaged 
10  cents  per  yard  per  year. 

Contrary  to  the  general  belief,  cobblestone  does  not  stand 'well 
under  heavy  traffic.  There  is  not  sufficient  stability  in  the  stones 


164        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

to  stand  the  blows  they  are  subjected  to,  and  the  results  is  that  they 
are  knocked  out  of  place.  Portions  of  several  cobble-paved  streets 
in  Brooklyn,  N.  Y.,  which  made  a  connection  between  granite  pave- 
ments over  which  a.  large  amount  of  traffic  was  carried,  cost  19 J 
cents  per  yard  per  year  for  repairs.  The  cost  of  repairs  for  nine 
years  was  enough  to  repave  them  with  granite  blocks  on  a  sand 
base. 

The  subject  of  repairs  of  asphalt  will  be  taken  up  in  another 
chapter. 

The  values  assigned  are:  granite  A  10,  granite  B  7,  asphalt  6, 
brick  6,  Belgian  7,  cobblestone  2,  and  macadam  3. 

Favordbleness  to  Travel. — This  is  a  difficult  property  to  reduce 
to  a  cash  basis.  Some  engineers  say  that  the  amount  of  noise  made 
by  driving  a  wagon  over  different  kinds  of  pavements  shows  the 
relative  amount  of  damage  caused  to  the  wagon.  While  this  may 
seem  a  strange  standard,  it  is  a  logical  one,  as  it  is  well  known  that 
the  smoother  the  pavement  the  less  noisy  it  is. 

In  response  to  an  inquiry  as  to  the  difference  in  wear  and  tear 
to  delivery-wagons  and  horses  when  the  asphalt  pavements  of 
Brooklyn,  N.  Y.,  were  increased  from  15  to  65  miles  in  a  total 
pavement  mileage  of  about  500,  two  of  the  largest  dry-goods  firms 
said: 

"We  desire  to  say  that  there  is  a  very  appreciable  difference 
in  our  wear  and  tear  account  since  the  increase  of  asphalt  pave- 
ments. No  more  damage  has  been  done  to  our  horses,  and  of  course 
it  goes  without  saying  that  the  saving  to  wagons  must  be  very 
great/' 

"We  beg  to  state  that  the  effect  of  the  pavements  of  this 
Borough  has  been  of  such  a  character  as  to  save  us  considerable 
wear  and  teap  on  our  wagons,  and  lameness  to  our  horses/5 

In  1896  the  Poughkeepsie  Cab  and  Transfer  Co.  said  in  answer 
to  an  inquiry:  "  We  would  say  that  our  repair  bill  for  1895  was 
50  per  cent  less  than  in  1894,  and  our  shoeing  bill  42  per  cent  less 
in  1895  than  in  1894.  We  attribute  this  in  a  great  measure  to 
the  introduction  of  smooth  pavements  in  our  city/'  Poughkeepsie 
at  that  time  had  about  28,000  square  yards  of  asphalt  block  pave- 
ment. 


THE  THEORY  OF  PAVEMENTS.  ]  G5 

In  1889  the  following  two  questions  were  put  to  the  omnibus- 
drivers  of  London: 

1st.  Which  do  you  consider  the  best  form  of  roadway  to 
drive  over? 

2d.  Which  the  worst? 

The  answers  were: 

1st.  750  wood;   219  macadam;   197  granite;    51  asphalt. 

2d.  122  wood;   1  macadam;   13  granite;   1045  asphalt. 

It  must  be  remembered,  however,  that  the  asphalt  pavement 
is  that  laid  of  natural  rock  and  probably  subjected  to  as  bad  a 
climate  for  slipperiness  as  that  of  any  city  in  the  world. 

The  condition  in  which  a  pavement  is  kept  affects  different 
pavements  differently.  An  editorial  note  in  Engineering  in  1876 
says:  "  Cornhill  was  blocked  for  nearly  an  hour  through  the  falling 
of  horses,  and  the  scenes  in  Cheapside,  Eastcheap,  Mowgate  Street, 
are  simply  disgraceful,  not  from  the  fault  of  the  paving  of  the 
roadway,  but  simply  because  it  is  not  kept  clean."  This  referred 
to  asphalt.  The  values  given  to  different  pavements  are:  granite  A 
3,  granite  B  2,  asphalt  5,  brick  4,  Belgian  2,  macadam  5^,  and  cob- 
blestone 0. 

Sanitariness. — There  is  a  great  difference  in  the  sanitary  value 
of  the  pavements  in  question.  The  committee  of  the  Society  of 
Arts  of  London  elsewhere  referred  to  made  the  following  statement 
on  this  point: 

"  In  urban  districts  which  have  been  well  drained  with  proper 
self-cleansing  «ewers  and  freed  from  emanations  from  them,  fever 
has  been  found  to  lurk  in  those  quarters  where  the  surface  paving 
and  surface  cleaning  are  bad.  On  the  other  hand,  the  extension  of 
impermeable  pavements  alone,  other  conditions  as  to  drainage,  etc., 
remaining  the  same,  has  been  attended  with  a  marked  reduction  of 
malarious  disease." 

At  the  time  of  the  cholera  in  London  in  1848,  it  being  impos- 
sible to  clean  the  cobble-paved  streets,  the  Board  of  Health  covered 
the  surface  with  3  inches  of  clean  earth. 

"  As  a  sanitary  rule  perfect  impermeability  of  street  covering 
is  of  primary  importance." 

These  principles  are  unquestionably  correct.    And  consequently 


166        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

asphalt  with  its  smooth,  impermeable  surface  ranks  very  high. 
Granite  A  and  brick  also  resist  moisture.  But  they  are  more  noisy, 
and  noise  must  be  considered  under  this  head.  Noisy  streets  affect 
one's  nervous  system,  and  a  noisy  pavement  is  poorly  adapted  for 
streets  near  hospitals,  schools,  and  similar  buildings,  whatever  may 
be  their  qualities  in  other  respects.  Granite  B  and  Belgian  have 
joints  filled  with  sand  which  is  partially  swept  out  and  replaced 
with  street  refuse  of  all  kinds.  Decaying  as  it  must,  it  is  always 
offensive  and  unhealthy.  The  sand  joints  also  allow  moisture  to 
accumulate,  which  is  a  source  of  disease.  A  cobblestone  pavement 
can  never  be  kept  clean.  To  make  it  so  it  would  be  necessary  to 
remove  all  the  supporting  material  between  the  stones,  and  the 
result  would  be  a  collection  of  loose  rocks. 

Macadam  is  always  dusty  if  not  thoroughly  and  frequently 
sprinkled.  It  absorbs  and  gives  off  moisture  readily  and  should 
not  be  considered  as  a  street  pavement,  although  it  ranks  high  in 
some  respects. 

In  the  old  city  of  New  York  the  number  of  deaths  in  1892  was 
44,329;  in.  1893,  44,486;  in  1894,  41,175;  in  1895,  43,420;  in 
1896,  41,622;  in  1897,  38,877;  in  1898,  40,240;  and  in  1899, 
39,822, — showing  an  absolute  decrease  of  4507  despite  the  large 
increase  in  population.  This  is  a  remarkable  record.  It  can  be 
accounted  for  in  part  by  increased  sanitary  measures  in  general, 
and  largely  by  the  laying  of  asphalt  pavements  on  the  east  side  in 
the  tenement  district,  where  the  population  is  denser  per  acre  than 
in  any  other  city  of  the  world.  The  streets  have  been  kept  clean 
and  have  served  largely  as  recreation-grounds  of  the  people  in  the 
evenings  and  on  Sundays.  As  a  sanitary  pavement,  then,  granite  A 
receives  9,  granite  B  7,  asphalt  13,  brick  11,  Belgian  5,  macadam  5, 
and  cobblestone  2. 

Having  now  discussed  each  property  which  is  possessed  by  a 
pavement  and  assigned  to  each  its  proper  percentage  value,  as  well 
as  considered  each  pavement  in  relation  to  these  different  values, 
it  will  be  possible  to  construct  a  table  that  will  show  in  detail  how 
each  material  stands  relatively  to  any  other,  and  also  what  propor- 
tion of  the  properties  of  a  perfect  pavement  is  possessed  by  each 
pavement  under  consideration. 


THE  THEORY  OF  PAVEMENTS. 
TABLE  No.  54. 


16' 


0 

a 

< 

9 

pq 

3 

« 

i 

\ 

1 

0 

§ 

§ 

"a. 

"y 

§ 

i 

IS 

PH 

c 

0 

< 

« 

M 

& 

0 

Ohcapness         . 

14 

2 

4 

4 

3 

5 

7 

Durability    

21 

21 

17 

15 

13 

17 

7 

15 

Easiness  of  cleaning    .... 

15 

11 

8 

15 

12 

7 

5 

2 

Li^ht  resistance  to  traffic. 

15 

n 

6 

15 

12 

6 

6 

4 

Nou-  slipperiness 

7 

u 

5 

3 

0 

3 

7 

5 

K;i><;  of  iiic'iiutciKUicc 

10 

10 

7 

6 

6 

7 

3 

2 

Fuvorableness  to  travel.  .  . 

5 

3 

2 

5 

4 

2 

5 

0 

•Sanitaria  ess  

13 

9 

7 

13 

11 

5 

5 

2 

Total  

100 

69 

56 

76 

67 

52 

45 

44- 

Making  asphalt  the  standard  at  100,  the  values  of  the  others  will 
be:  granite  A  91,  brick  88,  granite  B  74,  Belgian  68,  macadam  59, 
-and  cobblestone  58. 

This  table  is  original  and  has  been  made  up  after  much  careful 
study.  It  is  not  supposed  to  be  infallible,  nor  always  exact,  as 
much  of  it  has  been  determined  by  individual  judgment.  What  is 
•claimed  for  it  is  that  it  is  working  on  the  right  lines  in  attempting 
to  express  positively  what  is  generally  given  in  very  general  terms. 
By  a  proper  understanding  and  use  of  it  an  intelligent  student  can 
apply  the  principles  used  in  its  construction  to  any  particular  case 
that  may  present  itself,  and  when  he  comes  to  a  conclusion  be  able 
to  defend  himself  with  logical  arguments. 

Its  working  can  be  illustrated  in  several  ways. 

Assume,  for  instance,  a  street  over  which  the  traffic  must  be 
heavy  and  continuous.  Ultimate  cost  is  of  great  importance.  It 
overrules  first  cost.  Light  resistance  to  traffic  and  foothold  for 
horses  are  ruling  elements,  so  that  a  given  power  may  move  its 
maximum  load.  The  items  first  to  be  studied  are,  then:  Dura- 
bility, maintenance,  traction,  and  the  non-slippery  property.  Con* 
suiting  tfhe  table  and  combining  the  values  for  these  items,  granite 
A  has  a  value  of  44,  granite  B  35,  asphalt  40,  brick  37,  Belgian  33, 
macadam  23,  and  cobblestone  26. 

Granite  A  has  such  a  decided  advantage  over  this  that  further 
study  is  not  necessary  to  come  to  a  proper  decision.  But  when  the 


168        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

figures  are  as  close  as  the  next  three,  ranging  from  40  to  35,  a  care- 
ful examination  of  the  remaining  properties  would  be  required. 
In  this  particular  instance  granite  A  ranks  so  high  in  the  totals,, 
and  so  far  ahead  in  the  special  requisites,  that  it  would  seem  that 
no  mistake  could  be  made  in  selecting  it  for  the  material  to  be 
used. 

Consider  next  a  residential  street,  built  up  with  homes  whose 
owners  have  means  sufficient  to  afford  the  best  of  anything  they 
desire,  and,  while  not  wishing  to  be  extravagant,  do  want  and  ex- 
pect the  best  pavement  that  can  be  laid  without  regard  to  expense. 

This  is  an  entirely  different  proposition.  Cost,  durability,  and 
maintenance,  so  important  before,  can  be  left  out  of  consideration 
altogether.  Easiness  of  cleaning,  non-slipperiness,  favorableness- 
to  travel,  and  sanitariness  are  the  governing  characteristics. 
Working  as  before,  granite  A  has  29,  granite  B  22,  asphalt  36,. 
brick  33,  Belgian  18,  macadam  12,  and  cobble  9. 

Asphalt,  possessing  all  the  desired  properties  in  so  high  a  degree,, 
should  be  selected  without  much  question. 

It  may  be  said  that  durability  and  maintenance  are  too  hastily 
disposed  of,  and  that  by  considering  them  the  results  would  be 
changed.  But  this  is  the  point  of  the  selection.  The  property  owners, 
can  afford  the  best.  They  would  not  carpet  their  parlors  with 
hemp  or  matting  because  it  would  last  longer  than  tapestry,  nor 
furnish  their  dining-room  table  with  crockery  and  pewter  rather 
than  with  china  and  silver.  The  problem  is  to  select  the  best, 
material  under  existing  conditions. 

The  above  conclusions  would  generally  hold  good  for  the  best 
retail  streets. 

Next  consider  a  residence  street  with  very  light  traffic,  where 
the  abutters  wish  a  good  but  an  economical  pavement,  one  that 
will  be  durable  and  as  near  the  best  as  their  financial  condition  will 
admit.  This  requires  careful  consideration.  The  destructive  action 
of  travel  is  almost  wholly  eliminated.  Durability  will  be  governed 
by  the  action  of  the  elements.  Every  quality  but  slight  resistance  to 
traffic  must  be  taken  into  account.  This  gives:  granite  A  62,  gran- 
ite B  50,  asphalt  61,  brick  55,  Belgian  46,  macadam  39,  and  cobble 
40.  Granite  A  leads  asphalt  by  1  point,  but  by  a  further  study  of 
the  table  it  will  be  seen  that  it  gets  its  supremacy  by  its  great  dura- 


TEE  THEORY  OF  PAVEMENTS.  169 

bility  under  traffic.  Eliminating  this  property,  granite  A  has  41, 
granite  B  33,  asphalt  46,  brick  42,  Belgian  29,  macadam  32,  and 
cobble  25.  All  but  the  three  leading  materials  can  now  be  re- 
jected, leaving  for  further  examination  granite  A,  asphalt,  and 
brick. 

Now  while  durability  has  been  eliminated,  its  value  was  deter- 
mined by  the  action  of  the  weather  as  well  as  traffic.  In  this  case 
the  latter  can  be  left  out,  and  when  it  is  remembered  that  asphalt 
has  a  life  that  is  determined  by  climatic  conditions,  irrespective  of 
traffic,  it  will  be  seen  that  granite  A  and  brick  in  this  instance  can 
consistently  be  placed  above  it.  These  two  have  now  practically  the 
same  standing,  but  by  a  further  examination  it  will  be  learned  that 
granite  A  gains  4  points  over  brick  on  maintenance  simply  by  its 
superiority  under  heavy  travel.  Leaving  that  out  of  the  total, 
granite  has  31  and  brick  36,  and  the  latter  is  plainly  the  selection 
to  be  made. 

If  the  property  owners,  however,  think  the  price  too  high,  and 
prefer  granite  with  its  inconveniences  to  the  more  pleasing  brick, 
then  granite  B  would  be  the  choice,  but  it  must  be  understood  that 
the  decision  was  reached  for  financial  reasons. 

Assume  next  that  a  country  highway  is  to  be  improved  where 
the  traffic  is  not  heavy,  but  the  road  is  needed  to  facilitate  the  inter- 
course between  towns,  or  to  connect  a  suburban  village  with  the 
parent  city.  Sanitariness,  easiness  of  cleaning,  durability  (except 
as  to  action  of  weather),  and  light  resistance  to  travel  can  be 
eliminated, — sanitariness  and  easiness  of  cleaning  because  on  a 
sparsely  settled  road  many  things  are  unimportant  that  could  not 
be  tolerated  in  a  city;  the  other  qualities  because  no  heavy  loads 
will  be  attempted.  There  will  remain,  then,  granite  A  21,  granite 
B  18,  asphalt  18,  brick  19,  Belgian  17,  macadam  22,  and  cobble  21. 
In  this  case  the  values  are  more  nearly  alike,  but  the  cost  of  the 
first  five  materials  will  rule  them  out  at  once.  There  can  be  no 
question  between  macadam  and  cobble  on  account  of  the  unde- 
sirability  of  the  latter,  even  though  the  former  has  but  one  point 
in  its  favor.  By  modifying  the  foundation  for  brick  under  these 
conditions,  it  would  make  a  good  showing,  and  in  many  localities 
prove  the  proper  material. 

The  above  examples  illustrate  the  workings  of  the  table,  show- 
ing how  it  is  possible  to  analyze  the  conditions  that  may  arise  in 


170        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

any  case,  and  how  easy  it  is  to  arrive  at  an  intelligent  and  logical 
result  when  a  systematic  investigation  is  undertaken. 

An  engineer  who  has  under  his  charge  the  maintenance  and  re- 
newal of  a  large  amount  of  pavement  will  be  governed  by  slightly 
different  principles  from  those  just  laid  down.  He  will  have  a 
certain  sum  of  money  from  year  to  year  to  be  used  on  this  work, 
and  it  will  be  his  duty  to  make  the  most  of  it.  He  is  now  endeavor- 
ing to  benefit  the  entire  city,  not  the  residents  of  any  one  section, 
as  the  funds  for  this  purpose  are  raised  by  taxation  upon  the  city 
at  large.  He  should  be  governed  more  by  ultimate  economy  than 
iirst  cost.  He  must  take  into  consideration,  too,  the  interruption 
to  travel  by  too  frequent  repair  on  business  streets.  A  material 
that  might  be  figured  out  as  economical,  even  if  short-lived,  by 
reason  of  its  cheapness  both  of  first  cost  and  renewal,  might  re- 
quire so  much  attention  as  to  be  an  actual  nuisance  on  a  business 
thoroughfare.  An  engineer's  appropriation  is  generally  inadequate 
ior  his  work,  and  careful  study  is  necessary  to  bring  about  the  best 
Tesults.  The  smaller  the  amount  the  more  time  should  be  spent 
in  directing  its  expenditure.  An  eminent  authority  has  said  that 
if  one  has  but  five  minutes  in  which  to  perform,  a  difficult  task, 
three  minutes  should  be  consumed  in  ascertaining  how  to  do  it. 

The  engineer  who  occupies  such  a  position  will  find  himself 
confronted  with  an  interesting  and  ever-varying  problem.  Condi- 
tions are  constantly  changing,  traffic  is  divided,  and  circumstances 
keep  arising  that  require  his  faculties  to  be  ever  alert.  But  if  he 
meet  the  question  successfully,  and  ultimately  arrive  at  the  true 
solution,  his  satisfaction  is  as  great,  perhaps,  as  in  any  other 
branch  of  his  profession. 

In  estimating  the  life  of  a  certain  material  to  be  laid  on  any 
particular  street,  it  must  be  remembered  that  when  any  one  road  is 
selected  to  be  made  into  a  thoroughfare,  traffic  will  be  immediately- 
diverted  to  it  and  the  wear  of  the  pavement  abnormally  increased. 
Consequently  the  natural  life  of  the  material  must  not  be  judged 
Toy  its  wear  on  this  particular  street. 

Taking  now  the  costs  and  lives  of  the  different  pavements  as 
herein  deduced,  the  actual  annual  expense  of  each  for  a  period  as 
near  fifty  years  as  will  be  convenient  for  each  material  can  be 
easily  maintained  and  compared  by  the  formula 


THE  THEORY  OF  PAVEMENTS.  171 

r> 

A  -j-  CI  +  -T r  =  annual  expense. 

.zv 

For  granite  A:    (7  =  $2.50; 
/  =      .035; 
72=      .60 — an  amount  sufficient  to  relay  the 

pavement  once  during  life; 
A  =      .064; 
AT=  25  years. 

Substituting  in  the  equation, 

$0.06425  +  .0875  +  ^  =  $0.17575  for  first  period. 

For  the  second  period,  assuming  the  value  of  the  concrete  to 
be  $0.70  per  square  yard,  making  the  cost  of  relaying  $1.80  per 
yard,  the  annual  expense  is  found  as  before  to  be  $0.13326,  or  for 
fifty  years  an  average  of  $0.154. 

For  granite  B :    C  =  $1. 65 ; 

/  =      .035  as  before; 

R  =    0.25 — cost   of    relaying   pavement   once 

during  life; 
A  =  .05841; 
JV=  20  years. 

Substituting, 

.05841  +  .05775  -f  .0125  =  0.12866  for  first  period. 

For  any  subsequent  period  the  cost  will  be  the  same,  as  the  pave- 
ment has  no  appreciable  value  at  end  of  life. 

For  asphalt:  C  -  $1.75; 

/  =      .035; 

R  =    0.72; 

A  =      .0714; 

N  =  18  years. 
Substituting, 

$0.0714  -f  .06125  +  .04  =  $0.17265  for  first  period. 


172        STREET,  PAVEMENTS  AND  PAVING  MATERIALS. 


For  any  subsequent  period,  assuming  the  cost  of  repaying  to  be 
$1.25  per  square  yard,  the  expense  will  be  $0.1345  per  yard,  and  for 
fifty-four  years  an  average  of  $0.147. 

For  brick:  C  =  $2.00; 

/  =      .035; 

R  =      .60; 

A  =      .1036; 

JV  =  15  years. 
Substituting, 

0.1036  +  .07  +  .04  +  0.2136  for  first  period. 

For  any  subsequent  period,  assuming  cost  of  repaying  to  be 
$1.25  per  yard,  the  annual  expense  will  be  $0.1485,  or  an  average 
for  forty-five  years  of  $0.17  per  year. 

Table  No.  55  shows  the  above  results  condensed. 

TABLE  No.  55. 


Material. 

First  Cost 
per  Square  Yard. 

Expense  per  Yard 
for  First  Period. 

Expense  per  Yard 
for  50  Years. 

Granite  A.         .  .    . 

$2.50 

$0.17575 

$0.154 

Granite  B 

1  65 

0.12866 

0.12866 

Alphalt 

1.75 

0.17265 

0  147* 

Brick      

2.00 

0.2136 

0.170f 

*  54  years. 


1 45  years. 


In  1898  the  city  of  Minneapolis,  Minn.,  awarded  a  contract  for 
asphalt  pavements  for  $2.15  per  yard  with  a  ten  years'  guarantee,, 
and  an  additional  price  of  10  cents  per  yard  per  year  for  the  next 
ten  years  after  the  expiration  of  first  guarantee.  Assuming  the 
interest  charge  to  be  3J  per  cent,  and  the  bonds  to  mature  in 
twenty  years,  this  pavement  would  cost  15  cents  per  yard  for  the 
first  ten  years,  and  25  cents  per  yard  for  the  additional  period,  but 
with  no  other  charge,  except  for  maintenance,  for  the  remainder 
of  life. 

Table  No.  56  shows  the  pavement  mileage  of  eight  of  the  prin- 
cipal cities  of  the  country  on  January  1,  1900,  except  Washington, 
which  is  computed  for  July  1,  1899;  also  the  mileage  as  it  existed 
in  1890  except  as  noted.  This  table  is  given  to  show  the  change 


THE  THEORY  OF  PAVEMENTS. 


173 


In  character,  as  well  as  the  amount  of  pavement,  during  the  last 
•decade.  This  is  particularly  noticeable  in  the  case  of  Philadelphia, 
where  the  increase  has  been  328  miles.  Asphalt  has  increased  210.7 
miles,  stone  block  232.6  miles,  brick  99.7  miles,  and  macadam 
105.5  miles,  while  cobble  and  rubble  stone  pavements  have  de- 
creased 378.8  miles.  The  actual  amount  of  new  pavements  laid  in 
nine  years  was  666.9  miles,  not  including  streets  repaved  with  the 
same  material.  While  a  great  portion  of  this  work  was  done  at  the 
expense  of  the  street-railway  companies,  it  is  a  remarkable  record 
that  will  probably  never  be  equalled  by  any  other  city  in  the 
world. 

TABLE  Xo.  56. 


Brooklyn. 

Boston. 

Buffalo. 

Chicago. 

1890 

1900 

1891 

1900 

1890 

1900 

1890 

1900 

Asphalt  

10.85 
88.90 

289.21 

68.82 
159.95 
236.86 

4.65 
69.27 
5.95 

13.80 
86.97 
1.01 

106.  as 

140.69 

222.74 

104.50 

9.24 
23.10 

78.60 
29.77 

Stone  block 

Cobblestone  

"   !07 
3.28 

"'if.47 
3.08 

Brick        

3.78 
78.57 

0.35 
204.57 

0.80 
280.57 

227.01 

29.51 
363.40 

Macadam        

2.81 

Coal-tar  and  concrete 

Sla^  block 

Wood      

410.29 

763.21 
4.88 

1269.37 

Miscellaneous        . 

Total  

386.77 

284.79 

547.97 

383.15 

250.07 

337.79 

669.64 

New  York. 

Philadelphia. 

St.  Louis. 

Washington. 

1890 

1900 

•  1891 

1900 

1890 

1900 

1890 

1900 

Asphalt  

16.34 
273.75 
3.33 

162.44 
272.73 
1.10 

43.4 
119.6 
375.1 
115.5 
19.8 
88.8 

254.1 
352.2 
69.2 
43.3 
119.5 
193.5 

3.95 
42.46 

11.81 
50.36 

51.80 
23.50 
11.50 

129.27 
27.19 
11.31 

Stone  block  
Cobblestone  .      ... 

Bubble-stone 

Brick  

1.10 
118.12 

14.23 
351.92 

'"s.w 

38.21 

0.40 
34.39 
14.08 

Macadam 

24.23 

290.08 

Coal-tar  and  concrete.. 

Granolithic  

12.8 

S'ag  block  

5.6 

Wood 

08 

5.26 
341.75 

6.89 
435.21 

0.30 
133.31 

216^ 

Total  

1050.2 

317.65 

550.57 

762.2 

In  the  eight  cities  mentioned,  asphalt,  stone-block,  and  brick 
pavements  have  increased  from  1043  miles  to  2,195  miles,  or  111 
per  cent;  while  stone  block  has  increased  from  776  to  1084  miles, 
or  39  per  cent;  asphalt  has  increased  from  246  to  942  miles,  or 


174        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

283  per  cent,  and  brick  from  20 'miles  to  169  miles,,  or  745  per  cent~ 
The  actual  increase  in  each  case  is: 

Miles. 

Stone    307 

Asphalt   696 

Brick    149 

Another  important  fact  will  be  observed  from  this  table:  the 
increase  in  the  amount  of  asphalt  pavement. 

In  1890  there  were  246.26  miles  of  asphalt  in  these  cities,  ex- 
cept, as  noted  in  Boston  and  Philadelphia,  and  in  1900  this  mileage 
had  increased  to  941.58  miles.  These  figures  speak  more  forcibly 
than  any  other  words  can  as  to  the  popularity  of  this  pavement. 
Wood,  it  will  be  noticed,  has  never  been  used  to  any  extent  in  any 
of  these  cities,  except  in  Chicago,  where  it  has  increased  about  350 
miles.  Brick  has  had  a  great  increase  in  Philadelphia,  and  has  been 
introduced  in  several  others. 

Openings  in  Pavements. 

One  of  the  great  sources  of  trouble  to  pavements  is  the  fre- 
quent cuts  made  in  it  for  repairs  and  connections  to  subsurface 
construction.  Fifteen  years  ago  it  was  thought  that  when  water, 
sewer,  and  gas  mains,  with  house  connections  to  each  lot,  were 
laid  in  a  street,  it  would  be  tolerably  free  from  disturbance  for  some 
years.  But  in  the  days  when  telegraph,  telephone,  and  electric- 
light  wires  are  required  to  be  placed  underground,  when  pipes  for 
heating  and  refrigerating  purposes  are  being  laid  in  our  public/ 
streets,  when  changes  in  and  repairs  to  street-railway  construction 
are  constantly  going  on,  it  seems  as  if,  in  many  cases,  a  pavement 
is  hardly  free  from  the  contractor  before  it  is  being  torn  up  by  the 
corporation  or  the  plumber. 

This  matter  is  very  difficult  to  regulate,  especially  when  so  many 
changes  and  improvements  are  being  made  in  subsurface  construc- 
tion. It  'would  seem,  however,  that  the  best  way  to  prevent  streets 
from  being  torn  up  is  to  provide  for  all  underground  construction 
before  the  pavement  is  laid,  and  then  give  no  permits  for  openings 
within  a  stipulated  time  except  in  extreme  cases.  When  a  street 
is  ordered  improved,  every  householder  on  the  line  of  improvement, 
and  every  corporation  having  any  property  at  present  or  in  pros- 


THE  THEORY  OF  PAVEMENTS.  175 

pective  on  the  street,  should  be  notified  to  make  all  needed  repairs 
or  extensions  at  once,  under  a  penalty  of  a  refusal  to  grant  per- 
mits for  extensions  for  a  term  of  years.  All  repairs  should  be 
hedged  with  such  conditions  and  requirements  as  to  make  it  so  ex- 
pensive that  corporations  would  find  it  to  their  interest  to  make  all 
possible  repairs  in  advance. 

If  a  new  building  be  constructed  on  a  paved  street,  it  must  have 
connections  to  the  different  street  mains.  If  these  sewers  have  not 
been  previously  laid,  the  pavement  must  be  opened. 

The  city  of  Kochester  has  the  power  to  construct  sewers  with 
their  attendant  connections,  lay  water-services,  etc.,  under  the  same 
contract  by  which  the  pavement  is  laid,  and  assess  the  cost  against 
the  abutting  property.  Corporations  having  or  projecting  subways 
for  any  purpose  are  compelled  to  construct  them  in  advance  of  the 
pavement. 

It  often  happens,  however,  in  most  cities,  that  real-estate  owners, 
are  so  anxious  to  increase  the  value  of  and  sell  their  property  that 
pavements  are  laid  far  in  advance  of  any  subsurface  construction. 

When  the  work  of  pipe-laying  comes  to  be  carried  out,  the  pave- 
ment is  badly  damaged  and  in  many  cases  practically  destroyed. 

In  the  report  of  the  Commissioner  of  Public  Works  for  New 
York  City  for  1896  it  is  stated  that  during  the  year  one  mile  in 
four  of  the  paved  streets  was  torn  up  for  construction  purposes, 
and  that  59,000  separate  openings  requiring  repairs  to  pavements 
were  made  during  the  year,  or  one  opening  for  every  40  feet  of 
paved  streets.  In  Brooklyn,  K  Y.,  during  the  year  1896  35,000 
openings  were  made  in  the  streets  of  the  city,  or  one  opening  for 
about  every  75  feet  of  paved  streets. 

In  the  report  of  the  Street  Department  of  Boston  it  is  said,  that 
for  the  year  ending  January  31,  1898,  14,017  separate  openings 
were  made  in  the  streets,  with  a  total  length  of  openings  of  213.4 
miles. 

These  figures  are  startling,  but  would  probably  be  duplicated 
in  every  large  city  in  the  country  in  proportion  to  its  size.  It  is 
true  that  the  repairs  are  made  at  the  expense  of  the  corporation  or 
plumber  rather  than  at  the  cost  of  the  city  at  large,  but  it  must- 
be  remembered  that  the  money,  in  every  instance,  comes  event- 
ually from  the  people,  and  that  with  proper  precaution  a  very  large 


176        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

portion  of  it  could  be  saved.  When  methods  of  construction  have 
been  developed  and  fully  standardized,  and  when  the  requirements 
of  modern  civilization  in  regard  to  public  wants  and  necessities 
have  been  fully  satisfied,  it  is  to  be  hoped  that  this  condition  of 
affairs  will  be  greatly  improved.  In  the  mean  time  every  effort 
should  be  made  to  have  the  pavement  disturbances  as  few  as  possi- 
ble, and  replaced  in  a  good  and  substantial  manner. 

It  is  almost  impossible,  however,  to  repair  any  opening  in  a 
pavement  so  that  it  will  be  as  good  as  before  disturbance.  The 
new  work  will  generally  be  a  little  above  or  below  the  old  surface, 
and  in  either  case  this  means  abnormal  wear.  Then,  too,  however 
well  the  pavement  may  be  laid,  any  settlement  in  the  earth  of  the 
€xcavation  results  in  a  corresponding  settlement  of  the  surface 
unless  laid  on  a  base  of  sufficient  strength  to  span  the  opening  and 
sustain  the  load  by  its  transverse  strength.  It  was  the  practice  in 
Brooklyn,  N.  Y.,  for  some  time  to  require  all  cuts  made  in  the  im- 
proved pavements,  whatever  the  original  foundation,  to  be  replaced 
on  a  Portland-cement  concrete  base  eight  inches  thick.  Settle- 
ments under  this  rule  were  very  rare. 

Stone  pavements  on  a  sand  base  must  always  be  relaid  over  con- 
nections with  an  allowance  for  future  settlement,  else  a  depression 
will  certainly  develop  over  the  trench,  requiring  relaying.  In  the 
event  of  the  former  method,  the  ridge  in  the  pavements  is  objec- 
tionable until  it  reaches  its  permanent  position,  and,  unless  the 
paver  be  possessed  of  rare  judgment,  it  will  alwa}^s  require  some  re- 
adjustment. This  will  increase  greatly  the  wear  of  the  material 
and,  consequently,  decreases  the  life  of  the  pavement. 


CHAPTER    VII. 

COBBLE    AND    STONE-BLOCK    PAVEMENTS. 

"WITHOUT  doubt  pavements  originated  from  the  necessity  of  im- 
proving low  places  in  roads,  which  become  impassable  in  wet 
weather  on  account  of  the  traffic.  This  was  done  successfully,  and 
seemed  so  desirable  that  when  traffic  increased  the  pavement  was 
extended,  and  in  time  it  became  a  necessity  over  the  entire  road. 
To  the  ancient  Romans  must  be  given  the  honor  of  being  the  first 
to  construct  roads  in  Europe  on  any  general  system,  and  to  their 
credit  be  it  said  that  the  work  was  done  in  a  thorough  and  sub- 
stantial manner.  These  old  Roman  roads  were  practically  works  of 
solid  masonry  construction,  built  of  irregularly  shaped  stones,  but 
finished  to  a  smooth  and  true  surface.  A  full  description  of  the 
method  of  construction  of  one  of  these  is  taken  from  the  French 
Encyclopedia  of  1836. 

"  1st.  A  cement  of  chalk  and  sand  one  pouce  in  thickness. 

"  2d.  On  this  cement,  for  the  first  bed,  large  stones  six  pouces 
thick  were  placed  on  one  another,  and  backed  by  hard  mortar. 

"3d.  A  second  bed,  eight  pouces  thick,  of  small  round  stones, 
mixed  with  other  broken  pieces  of  building  material  not  so  hard, 
and  mixed  with  a  binding  cement. 

"  4th.  A  third  bed,  one  foot  of  cement,  made  of  rich  earth 
mixed  with  chalk." 

An  ancient  pouce  was  1.09  inches,  and  an  ordinary  pouce  1.06. 
Fig.  3  shows  the  ground-plan  of  a  Roman  road  on  the  Septimer,  as 
taken  from  a  consular  report.  Figs.  4  and  5  show  sections  of  other 
Roman  roads. 

The  Romans  constructed  these  roads  all  over  their  conquered 
provinces,  and  in  after-times  the  discovery  of  their  remains  was 
taken  as  proof  of  former  Roman  occupation.  That  the  Romans' 
work  was  well  done  is  shown  by  the  roads  themselves,  as  the  one 

177 


178        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

previously  described  is  said  to  have  been  in  good  condition  fifteen 
centuries  after  it  was  built. 


FIG.  4 


FEET 
METRES 


Gravel  bound  in  rement  mixed  with  Chalk 
^ 
iRiclTEarth  n 

-O^U^HJt*-<l»-uw.f>  __.. 

lit?  Cemeii 


FIG.  5. 

The  early  pavements,  however,  were  constructed  in  a  different 
manner,  the  material  being  in  almost  every  case  what  is  now 
termed  cobblestone.  This  was  natural,  as  the  cobblestones  were 
the  most  available,  and  were  known  to  have  great  durability.  As 
cities  grew,  and  the  needs  and  desires  for  better  streets  increased, 
the  rough  cobblestone  did  not  satisfy  the  people,  and  improved 
methods  were  demanded.  Attempts  were  then  made  to  construct  a 
smoother  pavement  by  forming  the  stones  into  rude  irregular 
blocks,  at  first  of  no  particular  shape,  but  endeavoring  to  give  a 
comparatively  smooth  surface.  This  was  the  beginning  of  the 


COBBLE  AND  STONE-BLOCK  PAVEMENTS. 


179 


modern  block  pavement.    As  time  passed  on,  the  blocks  were  made 
better  and  the  pavements,  consequently,  were  improved. 

In  Europe,  in  many  cities,  the  blocks  were  made  several  square 
feet  in  area,  and  at  first  were  laid  lengthwise  of  the  street,  but  as 
traffic  increased  it  was  demonstrated  that,  the  long  joints  being 
parallel  to  the  wheel  traffic  wore  rapidly,  and  the  pavement  soon 
became  rough  and  uneven.  To  obviate  this,  the  blocks  were  made 
square  and  were  laid  as  is  shown  in  Fig.  G,  which  shows  a  recent 


SIDEWALKS 


street  in  Catania,  Italy.  These  blocks  are  of  hard  lava,  16  x  20  inches 
square  and  8  inches  thick.  It  was  soon  discovered,  also,  that  these 
large  blocks  were  not  suitable  for  heavy  traffic.  It  was  difficult  to 
get  them  so  bedded  on  any  foundation  that  they  would  maintain 
their  position  under  heavy  loads,  and  the  blocks  themselves  soon 
hecame  displaced.  This  caused  the  blocks  to  be  made  smaller  still, 
and  the  greater  portion  of  the  European  cities  adopted  a  block 
about  6x8  inches  square,  and  of  depths  varying  according  to  traffic. 
In  this  country,  however,  the  original  pavements  were  all  of 
cobble.  The  cities,  as  a  rule,  were  poor,  the  cobblestones  were 
available  and  naturally  came  into  quite  common  use.  They  gave 
very  good  service,  but  were  necessarily  rough,  uneven,  and  very 
noisy.  The  Russ  blocks  spoken  of  in  a  previous  chapter  were 
probably  the  only  large  square  blocks  that  were  ever  laid  in  an 


180        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

American  pavement  to  any  great  extent,  though  some  were  used  in 
New  Orleans  and  Boston. 

Following  the  cobblestone,  and  in  response  to  the  demand  for 
an  improvement  on  them,  came  what  has  always  been  known  in  this, 
country  as  the  Belgian  block.  The  name  is  given  to  it  because  it 
was  first  used  in  Belgium,  and  it  came  to  be  quite  generally  adopted 
in  Europe.  In  shape  it  was  a  truncated  pyramid,  with  base  about 
5  or  6  inches  square,  and  a  depth  of  from  7  to  8  inches,  the  bottom 
of  the  block  being  of  dimensions  not  more  than  1  inch  different 
from  the  top.  This  was  an  improvement  on  the  cobblestone,  and 
when  well  shaped  and  of  proper  material  made  a  very  good  pave- 
ment. In  New  York  and  vicinity  it  became  quite  popular  soon 
after  its  adoption,  about  1850.  The  trap-rock  forming  the  Pali- 
sades of  New  Jersey  is  easily  cut  into  blocks  of  this  shape,  and 
being  so  near  New  York,  it  makes  a  very  cheap  and  durable  pav- 
ing material.  As  the  blocks  became  more  common,  deviations, 
were  allowed  from  the  specifications,  and  the  resulting  blocks  were 
too  small  on  the  base  to  allow  a  solid  bearing,  and  under  traffic 
they  soon  got  out  of  position,  and  in  consequence  the  pavement  be- 
came rough.  An  improvement  on  the  Belgian  block  was  to  make 
the  block  an  exact  cube.  This  was  done  in  the  old  country,  and 
many  cities  there  at  the  present  time  lay  blocks  that  are  of  that 
shape. 

The  question  of  proper  paving  material  became  of  so  much  pub- 
lic importance  in  Philadelphia  that  in  1843  a  committee  of 
eminent  engineers  was  appointed  by  the  Franklin  Institute  to  ex- 
amine into  the  subject  and  make  a  report  upon  the  best  material 
for  the  city  of  Philadelphia  to  adopt.  After  a  very  careful  and 
thorough  investigation  of  the  material  being  used  both  in  this 
country  and  in  Europe  at  that  time,  the  committee  made  an  ex- 
haustive report  to  the  society.  After  speaking  o-f  several  experi- 
ments of  different  kinds  that  had  been  made  in  the  city,  and  show- 
ing where  they  were  faulty,  they  finally  made  tlhe  following  recom- 
mendations for  the  material  to  be  adopted  for  the  Philadelphia 
streets. 

Streets  of  the  First  Class. — These  should  be  paved  with  dressed 
stone  blocks  laid  in  diagonal  courses  to  the  street,  upon  a  subpave- 
ment  of  pebbles.  These  blocks  were  to  be  exactly  8  inches  deep  and 
from  7  to  9  inches  wide,  and  8  to  10  inches  long.  The  estimated 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  181 

cost  of  this  pavement  at  that  time  was  $3  per  square  yard.  This 
pavement  was  recommended  for  streets  of  heavy  traffic  when  the 
grade  was  2n/10  per  cent  or  less. 

Streets  of  the  Second  Class. — The  pavement  for  these  streets 
should  consist  of  two  stone  tramways  built  in  each  street  to  accom- 
modate traffic  in  both  directions,  and  the  spaces  between  the  trams 
and  curbs  to  be  paved  with  cobble.  It  was  estimated  that  this 
would  cost  for  laying  transversely  on  the  streets  already  paved,  and 
repaving  the  old  material,  about  $1  per  square  yard  over  the  entire 
surface  between  the  curbs. 

Streets  of  the  Third  Class,  including  all  Lanes  and  Alleys. — For 
this  the  then  method  of  paving  with  cobbles  was  recommended, 
adopting  the  improvements  suggested  in  the  report,  which  con- 
sisted of  using  more  regularly  formed  stones  and  thus  having  the 
average  depth  6  inches.  The  committee  reported  as  the  best  shape 
for  the  cobblestone  "  that  of  a  prolate  spheroid  generated  by  an 
ellipse,  of  which  the  major  axis  is  double  the  length  of  the  minor." 

A  tramway  street  similar  to  that  proposed  for  those  of  the  sec- 
ond class  had  been  laid  in  London  in  1825  on  the  Commercial 
Road,  and  the  Philadelphians  had  had  an  opportunity  of  seeing  one 
that  had  been  made  a  short  time  previous  to  1843  on  Arch  Street. 

How  much  attention  was  given  to  this  report  can  be  seen  from 
the  fact  that  in  1884  (forty-one  years  after  it  was  made)  ninety- 
three  per  cent  of  the  entire  pavements  of  Philadelphia  (535  miles) 
was  then  paved  with  cobblestone,  as  has  been  before  stated. 

It  did  not  require,  however,  many  years'  experience  with  Bel- 
gian blocks  to  demonstrate  to  New  York  City  that  the  proper  pave- 
ment had  not  yet  been  discovered,  and  many  experiments  were 
made  with  a  view  to  improvement.  About  1865  a  patent  was  issued 
by  the  United  States  to  Mr.  Charles  Guidet  for  laying  granite  pave- 
ments. The  distinctive  points  of  this  pavement,  and  upon  which 
Mr.  Guidet  based  his  patent,  were: 

First,  stones  bounded  by  six  faces,  the  two  opposite  faces  being 
parallel  with  each  other. 

Second,  the  width  of  the  joints  running  transversely  to  the 
street  is  comparatively  wide. 

Third,  the  width  of  the  joints  running  longitudinally  to  the 
street  is  comparatively  narrow. 


182        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Pavements  under  this  patent  were  laid  in  New  York,  and  sev- 
eral in  Brooklyn,  about  1869.  The  cost  of  those  laid  by  the  patentee 
was  about  $7  per  yard.  Not  thinking  the  patent  valid  or  equitable, 
the  city  of  Brooklyn  paved  several  streets  in  accordance  with  this 
method,  without  paying  any  royalty.  The  patentee  brought  suit, 
but  was  finally  beaten  in  the  United  States  court  and  the  case  dis- 
missed. This  was  the  first  attempt  made  in  this  country,  on  any 
extended  scale,  to  lay  pavements  of  oblong  blocks. 

The  different  kinds  of  stone  pavement  now  being  used  in  the 
United  States  are  the  cobblestone,  the  Belgian  block,  and  the 
oblong  block. 

Cobblestone. 

Fortunately  for  the  people  who  are  to  come  after  us,  very  little 
cobblestone  pa-venient  is  now  being  laid.  In  a  few  cities,  however, 
where  property  owners  pay  the  first  cost  of  the  pavement  and  are 
relieved  of  any  further  charge  for  its  maintenance  or  relaying,  its 
cheapness  is  a  sufficient  inducement  to  cause  it  to  be  used.  It  never 
gives  satisfaction,  and  is  really  only  a  substitute  for  a  pavement. 
If  laid  in  the  manner,  and  of  stone,  similar  to  that  described  by 
the  Philadelphia  committee,  a  tolerably  good  pavement  would  be 
secured,  but  all  stones  of  that  character  have  now  become  so  scarce 
that  to  secure  them  would  increase  the  cost  to  such  an  extent  as  to 
make  it  almost  equal  to  that  of  the  granite  pavements. 

Cobblestone  specifications,  too,  have  been  most  shamefully 
abused  and  violated.  As  pavements  of  this  class  increased  and  the 
demand  for  the  stones  became  so  great  that  suitable  ones  were  ob- 
tained only  at  considerable  expense  and  witjh  some  difficulty, 
almost  anything  in  shape  and  size  was  permitted  to  be  used.  The 
result  was  that  cobblestone  pavements  were  even  worse  than  they 
would  have  been  had  they  been  properly  laid.  Cobblestone  specifi- 
cations generally  provide  that  the  stones  shall  be  the  best  selected 
water  or  bank  cobblestones,  of  a  durable  and  uniform  quality,  with 
round  heads  and  well-shaped  large  ends.  They  shall  not  be  less 
than  4  inches  nor  more  than  8  inches  in  diameter  across  the  head, 
nor  less  than  5  inches  nor  more  than  10  inches  in  depth;  no  tri- 
angular, split,  or  otherwise  ill-shaped  stones  can  be  used',  nor  any 
which  are  soft  and  rotten.  The  author,  once  examining  a  cobble 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  183 

street,  found  one  stone  of  such  size  that  he  decided  to  measure  it. 
It  was  3  ft.  10  in.  long  and  11  in.  wide,  and  was  probably  laid 
under  specifications  similar  to  the  above.  In  another  instance,  in 
repaying  a  cobble  street  with  granite  blocks,  a  boulder  was  found 
forming  part  of  the  pavement  which  was  so  large  that  it  could  not 
be  moved  without  blasting.  When  the  street  was  paved  originally, 
the  boulder  found  on  the  street  was  simply  lowered  in  position 
until  it  was  at  the  required  grade  for  the  pavement.  The  cobble- 
stone pavement  has  had  its  day  and  is  rapidly  passing  away,  but  it 
exists  at  the  present  time  in  such  quantities  that  it  will  require  sev- 
eral years  of  active  work  in  repaving  in  some  half  a  dozen  cities  to 
entirely  do  away  with  it.  Fig.  7  represents  a  section  of  a  cobble- 
stone pavement. 


FIG.  7. 

According  to  a  bulletin  issued  by  the  Department  of  Labor  in 
1899,  Baltimore,  Md.,  had  5,815,610  square  yards;  New  York  City, 
4,213,616  square  yards;  Philadelphia,  2,920,664  square  yards;  Cin- 
cinnati, 1,213,000  square  yards;  and  Pittsburg,  1,147,415  square 
yards  of  cobblestone  pavement. 

In  this  chapter,  and  in  the  entire  work,  where  estimates  are 
given  for  costs  of  any  kind  of  pavement,  the  street  is  supposed  to 
be  graded  to  subgrade,  and  any  cost  of  putting  it  in  this  condition 
must  be  added  to  the  prices  herein  given.  It  is  customary  for  pav- 
ing contractors  in  and  about  New  York  City  to  deliver  paving  ma- 
terial on  the  street  and  pile  it  compactly  on  the  sidewalks  before 
the  work  of  paving  is  begun.  The  foundation  is  prepared  and 
laborers  called  "  stone-chuckers  "  are  employed  to  carry  the  stones 
from  the  side  to  the  pavers.  The  organization  of  a  gang  for  laying 
cobblestone  pavement  is  as  follows:  One  foreman,  four  pavers,  two 
rammersmen,  four  chuckers,  two  men  preparing  sand  base,  and  two 
men  spreading  sand  on  the  completed  work.  This  gang  will  lay, 
under  favorable  conditions,  400  square  yards  per  day. 


184        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

Assuming  the  wages  as  follows: 

1  foreman           at  $3.50  per  day $  3.50 

4  pavers               "      4.50     "      "  18.00 

2  rammersmen  "      3.50     "      "  7.00 

4  chuckers          "      1.50     "      "  6.00 

4  laborers            "      1.25     "      "  .  5.00 


Total $39.50 

for  labor  for  laying  400  square  yards  of  pavement,  or  10  cents  per 
square  yard  for  labor. 

Assuming  sand  to  cost  $1  per  cubic  yard,  delivered  on  the  work,, 
and  that  1  cubic  yard  will  lay  5  square  yards  of  pavement,  and  that 
the  cobbles  themselves  will  cost  40  cents  per  square  yard,  the  total 
cost  for  material  will  be  60  cents  per  square  yard  plus  10  cents  for 
labor,  which  will  make  the  entire  cost  of  the  cobblestone  pavement 
70  cents  per  square  yard. 

In  making  any  estimate  upon  any  kind  of  pavement,  it  must  be 
remembered  that  the  cost  will  vary  a  considerable  percentage  ac- 
cording to  the  contractor,  one  man  making  a  paying  piece  of  work 
out  of  what  would  perhaps  be  a  losing  one  to  another.  The  prices, 
of  material,  too,  vary  considerably  even  in  the  same  city,  on  ac- 
count of  the  length  of  'haul,  and  other  local  conditions,  so  that  any 
estimate  must  be  considered  a  general  one  unless  special  conditions 
for  each  case  are  known. 

A  base  for  a  cobblestone  pavement  should  consist  of  no  less  nor 
much  more  than  6  inches  of  loamy  sand.  If  too  much  or  too  clean 
sand  be  used,  the  stone  will  become  loose  and  cannot  be  maintained 
in  position  under  traffic.  From  the  shape  of  the  stones,  there  is 
nothing  in  themselves  which  will  serve  to  bind  one  to  another,  so 
they  must  be  set  in  a  material  that  will  pack  solidly  and  remain  in 
position.  In  a  clean  sand  the  stones  will  roll,  and  when  no  other 
can  be  obtained  it  will  be  necessary  to  mix  it  with  a  certain  per- 
centage of  loam  in  order  to  get  satisfactory  results. 

Belgian  Block. 

This  pavement  in  New  York  and  vicinity  has  been  laid  almost 
entirely  with  the  trap-rock  from  the  Palisades  of  New  Jersey.  This 
rock  is  hard  and  durable,  but  after  some  wear  becomes  smooth  and 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  185 

slippery.  It  is  so  hard,  however,  that  when  properly  laid  it  will 
probably  last  longer  than  any  stone  that  is  brought  to  the  New 
York  market.  On  account  of  its  being  so  generally,  and  always  at 
first,  made  of  this  trap-rock,  all  trap-rock  pavements  have  been 
called  Belgian  pavements,  but  when  made  of  the  oblong  blocks 
similar  to  those  of  the  ordinary  granite  they  have  been  called,  in 
distinction,  u  specification  Belgian."  This  is  a  complete  misnomer, 
as  the  name  refers  distinctly  to  the  shape  and  not  to  the  character 
of  the  material,  as  some  Belgian  pavements  have  been  laid  of 
granite. 

One  great  objection  to  the  Belgian  pavement  is  that,  on  ac- 
count of  the  size  and  shape  of  the  blocks,  it  will  not  retain  its  form 
under  traffic,  except  upon  a  very  solid  foundation.  The  blocks,  too, 
are  of  such  size  as  to  give  a  poor  foothold  to  horses,  and  being 
square,  or  nearly  so,  there  is  always  a  considerable  length  of  joints 
that  is  parallel  to  the  line  of  the  wheel  traffic.  This  causes  the 
blocks  to  round  off,  wear  rough,  and,  at  intersections  where  traffic 
is  very  severe,  often  to  be  crowded  out  of  position  and  become 
rutted.  The  courses  in  this  pavement,  in  this  country  at  least,  have 
always  been  laid  parallel  to  or  square  with  the  street.  If  a  square 
blojk  is  to  be  used,  it  should  be  laid  in  courses  diagonal  to  the 
street  so  that  no  joints  should  be  parallel  to  the  traffic.  This,  how- 
ever, would  cause  some  extra  expense,  but  would  be  more  than 
made  up  in  the  benefit  that  would  be  derived  from  this  method. 
rn  this  country  the  Belgian  has  been  probably  laid  on  a  sand  base 
in  every  instance.  The  specifications  ordinarily  recite  that  tho 
stone  blocks  are  to  be  of  trap-rock,  of  durable  and  uniform  quality, 
each  measuring  on  the  base,  or  upper  surface,  not  less  than  6  nor 
more  than  8  inches  in  length,  and  not  less  than  4  nor  more  than 
6  inches  in  width,  and  of  a  depth  not  less  than  6  nor  more  than  8 
inches.  Blocks  of  4  inches  in  width  on  their  face  to  be  not  less 
than  4  inehes  at  the  base.  All  other  blocks  of  transverse  measure- 
ment on  the  base  to  be  not  more  than  1  inch  less  than  on  the  face, 
but  no  block  on  the  face  shall  be  ol  less  width  or  length  than  4 
inches.  Blocks  laid  along  curbs  must  in  all  cases  be  8  inches  in 
depth,  and  at  least  one-third  of  the  whole  number  must  be  of 
like  depth.  The  faces  of  the  blocks  must  be  smooth  and  free  from 
all  bunches  or  depressions. 


186        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

These  variations  allowed  in  the  size  and  shape  of  the  blocks 
make  it  very  difficult  to  get  a  pavement  in  which  the  courses  are 
true  and  the  joints  well  broken.  It  requires  constant  care  and 
watchfulness  on  the  part  of  the  inspector  to  see  that  blocks  in  the 
same  courses  are  of  the  same  width,  so  that  the  courses  may  run 
evenly  and  in  straight  lines  across  the  street,  and  at  the  same  time 
have  all  blocks  face  snugly  up  against  each  other.  After  the  blocks 
are  laid,  they  should  be  covered  with  sand,  which  must  be  swept 
into  the  joints  until  they  are  filled.  The  blocks  should  then  be 
rammed  to  a  firm  unyielding  bed  and  to  a  smooth  surface.  Wher- 
ever out  of  position,  the  blocks  should  be  trued  up  and  brought 
perpendicular  to  the  surface  of  the  street  and  covered  with  another 
coat  of  sand  and  thoroughly  rammed  the  second  time  until  <the 
pavement  is  solid  and  brought  to  a  proper  crown  and  grade.  Fig. 
8  represents  a  section  of  a  Belgian  block  pavement. 


FIG.  8. 

Another  form  for  blocks  of  trap-rock  has  been  used  in  New 
York.  The  blocks  are  practically  of  the  same  size  and  shape  as 
those  of  the  oblong  granite,  but  on  account  of  the  difficulty  of 
breaking  trap  they  are  not  generally  of  as  true  form.  Pavements 
laid  of  these  blocks  give  much  better  satisfaction  than  'those  of  the 
Belgian  and  are  very  durable.  They  are,  however,  subject  to  the 
same  fault  as  all  trap-rocks,  that  is,  of  becoming  extremely  slip- 
pery under  traffic.  While  used  to  quite  an  extent  in  New  York 
City,  they  are  not  being  laid  in  any  amount  at  present. 

On  a  piece  of  work  laid  of  this  material  the  organization  of  the 
gang  was  as  follows: 

5  pavers  at  $4.50  per  day $22.50 

3  rammersmen  "      3.50     "      "    10.50 

4  chuckers          "      1.50     "      "    8.00 

2  sandmen          "      1.25     "      «    2.50 

Making  the  total  for  labor $41.50 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  187 

This  gang  laid  350  yards  per  day.  The  blocks  o-f  which  the 
pavement  was  laid  cost  $37  per  thousand,  $4  for  freight,  and  $1 
for  hauling,  or  a  total  delivered  on  the  work  of  $42  per  thousand, 
or  42/10  cents  each.  The  blocks  laid  on  an  average  27  per  square 
yard.  In  this  particular  case  the  sand  was  obtained  adjacent  to  the 
street  and  practically  cost  nothing;  but  assuming  it  to  cost,  as  in 
the  case  of  the  cobble,  20  cents  per  square  yard,  the  total  cost  of 
the  pavement  will  be  for  350  yards: 

Labor $  41.50 

Blocks   3116  90 

Sand 70.00 

Total $508.40 

or  $1.43  per  yard.     The  street  where  this  work  was  done  was  44 
feet  wide. 

On  a  street  recently  paved  with  Belgian  blocks  the  pacing  gang 
consisted  of: 

4  pavers  at  $4.50  per  day $18.00 

2  rammers  "      3.50     "      "    7.00 

4  chuckers  "      1.50     "      "    6.00 

2  laborers  "      1.25     "  "    .                                         2.50 


Total $33.50 

The  amount  of  pavement  laid  per  day  was  240  yards,  or  a  cost  of 
14  cents  per  yard  for  labor.  The  stone  cost  about  $30  per  M  de- 
livered on  the  street,  and  thirty  blocks  laid  one  square  yard,  mak- 
ing the  entire  cost  of  the  pavement  per  square  yard; 

30  blocks  at  $30  per  M $0.90 

Sand    20 

Labor 14 

Total   $1.24 

As  the  Belgian  blocks  wore  smooth  and  became  rounded  off 
under  traffic,  considerable  dissatisfaction  arose  with  this  pavement, 
an'd  it  was  soon  seen  that  an  improvement  was  demanded  in  the 
shape  of  the  blocks.  Up  to  this  time  no  great  amount  of  granite 
had  been  used  in  street  pavements  in  this  country,  so  with  the  im- 


188        8TREET  PAVEMENTS  AND  PAVING  MATERIALS. 

proved  form  of  blocks  came  the  introduction  of  granite  as  a  pav- 
ing material.  The  first  pavement  laid  of  this  character  was,  as  has 
been  said  before,  the  so-called  Guidet  blocks,  but  these  were  large 
and,  while  durable  under  traffic,  soon  became  smooth  and  slippery. 
As  a  modification  of  this  all  the  blocks  were  changed  into  what  has 
generally  been  adopted  for  oblong  stone  blocks. 

Granite  Pavement. 

In  making  a  selection  of  stone  for  a  block  pavement,  the  hardest 
does  not  necessarily  give  the  best  results.  Any  hard  stone  wears 
smooth  and  becomes  slippery,  and  while  perhaps  it  is  the  most 
economical  for  the  severest  traffic,  under  medium  or  ordinary  ser- 
vice the  softer  stone  is  better.  The  hard  blocks  wear  on  the  edges, 
rounding  off  from  the  impact  of  the  horses'  shoes,  and  the  face 
becomes  smooth  from  the  abrasion  of  the  wheels,  so  that  in  a  few 
years  the  pavement  becomes  rough,  although  the  surface  of  the 
blocks  is  smooth.  A  good  example  of  this  is  the  pavements  that 
have  been  laid  in  Chicago  and  Omaha  of  the  so-called  Sioux  Falls 
granite,  described  in  Chapter  II.  It  is  extremely  durable  as  far 
as  abrasion  is  concerned,  but  cannot  be  considered  a  first-class  pav- 
ing material.  The  softer  granites  and  sandstones,  being  more 
tough,  do  not  break  on  the  corners  so  much,  but  wear  down  evenly 
and  smoothly  over  the  entire  surface  of  the  block,  so  that  the 
pavements  keep  moderately  smooth.  For  light  traffic,  and  per- 
haps anything  less  than  the  heaviest  traffic,  hard  sandstone  gives 
the  best  results.  Although  wearing  smooth,  the  character  of  the 
material  of  which  they  are  composed  prevents  them  from  being 
slippery,  so  that  while  they  may  wear  out  quicker  and  be  less  dur- 
able, while  they  are  in  use  the  pavement  is  much  better  for  gen- 
eral traffic. 

Limestone  blocks  have  been  used  very  little.  They  are  too 
soft  to  sustain  much  traffic  and  to  wear  evenly,  so  that  the  surface 
of  the  pavement  soon  becomes  rough  and  uneven.  In  certain  parts 
of  the  country,  too,  the  limestone  disintegrates  when  exposed  to 
the  atmosphere,  so  that  it  is  safe  to  say  that  the  only  proper  mate- 
rial for  the  stone-block  pavement  of  the  present  is  either  a  granite 
or  a  hard  sandstone. 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  189 

In  determining  upon  the  proper  dimensions  for  a  paving-block, 
several  questions  must  be  considered. 

Length. 

A  block  should  be  long  enough  to  give  a  firm  bearing  on  the 
foundation,  and  not  so  long  that  it  will  tip  up  under  traffic  or  fail 
to  conform  to  the  surface  of  the  street,  nor  so  short  as  to  make  too 
many  longitudinal  joints  or  present  too  small  a  surface  for  traffic. 

Width. 

The  blocks  should  be  made  of  such  a  width  as  to  give  a  good 
foothold  for  horses.  The  surface  of  the  block  itself  offers  but  a 
slight  foothold.  The  horse  must  depend  upon  the  shoe-calks  catch- 
ing on  the  transverse  joints  of  the  pavement,  so  the  width  of  the 
blocks  must  not  be  greater  than  the  difference  between  the  toe- 
and  heel-calks  of  the  ordinary  horseshoe,  thus  reducing  to  a  mini- 
mum the  tendency  to  slip.  On  the  other  hand,  the  blocks  must 
not  be  so  narrow  as  to  make  the  number  of  joints  too  many,  or  to 
make  the  face  so  small  as  to  render  the  block  unstable. 

In  specifications  adopted  for  paving  Havana  under  a  contract 
partially  entered  into  before  the  Spanish  war,  the  maximum  width 
of  blocks  was  made  3  inches,  on  account  of  mules  being  principally 
use*d  for  trucking,  and  their  feet  being  so  much  smaller  than  those 
of  the  ordinary  horse. 

Depth. 

In  determining  the  depth  of  the  block  two  principles  must  be 
considered:  first,  the  amount  of  wear  to  which  the  block  will  be 
subjected;  and  second,  its  stability.  Probably  very  few  granite 
pavements  are  worn  out  by  the  direct  action'  of  traffic  on  the  sur- 
face of  the  blocks.  They  become  rounded  off,  displaced,  and  worn 
in  parts  in  such  a  manner  as  to  make  the  entire  pavement  rough 
and  uneven  rather  than  from  any  direct  wear  of  the  block  itself. 
So  if  the  block  is  deep  enough  to  remain  firm  and  solid  in  its  posi- 
tion, it  will  generally  be  of  sufficient  depth  to  sustain  traffic.  As  a 


190        STREET  PAVEMENTS  AND   PAVING   MATERIALS. 

general  rule  no  block  should  be  laid  whose  depth  is  not  greater 
than,  and  preferably  1J  times,  its  width.  For  good  results  the 
minimum  depth  should  not  be  less  than  6  inches. 

The  exact  form  and  shape  of  the  blocks  have  a  great  deal  to  do- 
with  the  character  of  the  pavement,  and  a  good  surface  cannot  be 
obtained  from  poorly  shaped  blocks. 

The  specifications  of  blocks  in  the  Department  of  Highways, 
in  New  York  City  say  on  this  subject:  "  The  blocks  are  to  be  rect- 
angular on  the  tops  and  sides,  uniform  in  thickness,  split  and 
dressed  so  as  to  form,  when  laid,  close  joints,  with  a  fair  and  true 
surface,  free  from  bunches. 

The  Philadelphia  specifications  say  that  the  face  of  the  blocks- 
shall  be  not  warped,  parallel,  free  from  bunches,  depressions,  and 
inequalities  exceeding  J  of  an  inch. 

The  Clevejand  specifications  for  Medina  sandstone  blocks  sayr 
"  The  stone  to  have  parallel  sides  and  ends,  with  right-angle  joints,, 
any  roughness  and  points  on  stone  to  be  broken  off  so  that  when 
set  in  place  they  shall  have  tight  joints  for  the  distance  of  at  least 
3-J  inches  from  the  top  down.  The  area  of  the  bottom  of  any  stone 
to  be  not  less  than  f  of  the  area  of  the  top.  The  top  to  have  a 
smooth,  even  surface." 

The  London  specifications  say:  "Each  stone  to  be  properly 
squared  so  that  the  bottom  of  each  stone  shall  not  be  less  than  the 
top,  the  sides  and  ends  to  be  flat  so  as  to  remain  against  each  other 
throughout  the  whole  depth.  The  bottoms  of  the  stones  are  to»be 
flat,  and  the  tops  are  to  be  flat,  but  finished  rough." 

The  Glasgow  specifications  say:  "  Each  set  must  be  properly 
dressed,  squared  and  level  on  the  tops  and  beds,  the  sides  and  ends 
to  be  parallel  and  square.  The  sets  of  each  class  must  be  truly 
gauged;  no  bulges  or  hollows  will  be  allowed  on  any  pretext  what- 
ever." 

It  is  difficult  to  keep  the  contractors  to  the  above  specifications, 
as  the  block-makers  wish  to  work  in  all  blocks  possible  and  will  do 
their  utmost  to  have  them  admitted  even  if  they  do  not  conform  to 
the  specifications.  Some  granites  break  more  easily  than  others. 
Some  stone  that  is  naturally  hard,  tough,  and  very  durable  is 
bunchy  and  uneven,  so  that,  while  making  a  durable  pavement,  it  is 
rough  and  the  width  of  the  joints  is  apt  to  vary. 


Ipfc 

OF    THK 

UNIVERSITY 


COBBLE  AND  STONE-BLOCK  PAVEMENTS. 


191 


Table  Xo.  57  shows  the  dimensions  of  granite  blocks  used  on 
the  principal  streets  in  this  country  as  well  as  in  Great  Britain,  and 
Table  K"o.  58  shows  the  dimensions  of  blocks  used  in  the  principal 
cities  of  Europe. 

TABLE  No.  57. 


City. 

Length, 
Inches. 

Width, 
Inches. 

Depth, 
Inches. 

Remarks. 

Boston 

9  to  14 

3£  to  4^ 

7  to  8 

10  to  13 

3A  to  4 

6  to  6£ 

Cincinnati...  . 
New  York  .  .  . 
Philadelphia. 

St.  Louis    ... 
Edinburgh.  .  . 
GrlassiToW 

8  to  12 
8  to  12 
8  to  12 

9  to  12 
8  to  12 
6  to  9 

3  to4i 
3£  to  4£ 
81,  4, 
and  4£ 
3£  to  4| 
4 
3 

6  to  7 
7  to  8 
6to6i 

?i  to  81 
7 
5,  6,  7, 

6"  concrete  base 

6  to  9 

3i 

and  8 
5,  6,  7, 

t  ( 

3  to  4  in 

.  square 

and  8 
5  and  6 

1  < 

4 

4 

4 

3i 

tu 

First  class   6"  concrete  base 

3 

5 

Second  class,  6"  concrete  base 

London  

4 
5  to  12 

4 

3  or  less 

4 
9  to  9i 

Third  class,  10"  broken  -stone  base 
12"  concrete  base 

Montreal  

8  to  14 

3  to  4£ 

6    * 

Foundation. 

A  pavement,  as  is  true  of  every  other  work  of  construction, 
should  have  a  solid  foundation.  Without  it  it  is  impossible  to  keep 
the  blocks  in  position  and  thus  obtain  the  maximum  amount  of 
wear  from  the  pavement.  The  first  granite  pavements  were  laid 
on  a  sand  base,  but  as  traffic  increased,  both  in  kind  and  in  weight, 
it  was  found  necessary  to  give  the  blocks  a  more  solid  base,  and  a 
foundation  of  cement  concrete  was  adopted  in  heavy-traffic  streets. 
The  sand  foundation  is,  however,  being  used  at  present  with  good 
results  where  the  pavement  is  well  laid  and  on  light-traffic  streets. 

Preparing  the  Foundation. 

Whatever  the  base,  but  particularly  if  of  sand,  after  the  street 
is  put  to  subgrade,  the  entire  surface  of  the  roadway  should  be 
thoroughly  rolled  with  a  ten-ton  roller  until  it  is  solid  and  compact. 


192        STREET  PAVEMENTS  AND   PAVING  MATERIALS. 

TABLE  No.  58. 


City. 

Length, 
Inches. 

Width, 
Inches. 

Deptti, 
Inches. 

Remarks. 

Aix-la-Chapelle  

6| 

4 

7 

5|  to  6£ 

5£ 

51 

8  to  12 

3  to  6 

4  to  6 

7  to  71 

3£  to  4 

6J  to  7 

Basle       

7 

5 

6i 

Belfast    Ireland  

4 

4 

4 

«             « 

4 

4 

6 

Berlin  

7i  to  74 

74  to  71 

74  to  71 

134 

*  6f  * 

6  to  6^ 

7  to  9 

4  to  5 

7  to  8 

6  to  12 

3£  to  4£ 

6£  to  7 

Dresden  •] 

l£  times  J 
width   j 

5|  to  6f 

4f  to  5f 

6f  to  7£ 
51  to  6f 

First  class 
Second  class 

Dublin  

6* 

7 

4  to  54 
6i 
3i 

5^to5| 
6± 
6i 

Third  class 
Slag  blocks 

Flanders  

7  to  7  8 

7 

7 

ii 

6  to  7 

6 

6 

« 

5  7  to  6 

5  7 

5  7 

« 

4.7  to  5  7 

4  7 

4  7 

274 

lii 

7£ 

Grooved 

6 

6 

6 

7-| 

5i 

7 

Nuremberg  ••• 

6  to  8 

5£  to  6£ 

5|  to  6 

Paris         

9 

6i  to  9 

9 

Large 

6i  to  74 

5^  to  7 

6±  to  71 

Medium 

<  i 

6i  to  71 

4i  to  5| 

4ir  to  7 

Small 

18  to  24 

18  to  24 

8  to  10 

Square  blocks 

8 

6 

6£ 

St.  Gall,  Switzerland  

5| 
5| 
24  to  60 

5| 
4f 

12  to  18 

6ito7 
6±to7 
6  to  10 

134 

61 

6 

7i 

?! 

71 

Should  any  soft  spots  develop  that  will  not  become  solid  under  the 
roller,  they  must  be  excavated  and  refilled  with  firm  earth,  sand, 
or  gravel  and  then  thoroughly  rolled.  The  subgrade  should  be 
brought  to  the  exact  contour  as  specified  for  the  pavement  and  the 
required  depth  below  the  finished  surface.  The  sand  for  the  base 
should  be  next  spread  in  a  sufficient  quantity  and  the  paving-blo'cks 
laid. 

Laying  the  Blocks. 

A  few  engineers  recommend  that  the  blocks  should  be  laid  in 
uourses  diagonal  to  the  direction  of  the  street.    This,  however,  does 


CODDLE  AND  STONE-BLOCK  PAVEMENTS. 


193 


not  seem  to  be  good  practice,  as  it  does  not  give  as  good  a  foot- 
hold to  the  horses,  nor  will  the  blocks  wear  as  well  as  if  their 
courses  are  at  right  angles  to  the  street,  and  this  method  is  almost 
universally  adopted  at  the  present  time.  A  portion  of  Devonshire 
Street,  Boston,  is  now  paved  with  blocks  in  diagonal  courses. 
Originally  the  right  angle  method  was  continued  across  all  inter- 

A 


I.  .  I 


-\ 


]    .   I 


I       I 


FIG.  9. 

secting  streets.  This  was  all  right  for  travel  on  the  street  being 
paved,  but  it  was  all  wrong  for  the  cross-streets,  as  then  it  brought 
the  traffic  parallel  with  the  blocks,  and  they  soon  became  unduly 
worn  on  the  edges  and  the  pavement  became  rough.  This  method 
is  shown  in  Fig.  9.  To  remove  this  difficulty  the  plan  shown  in 
Pig.  10  was  adopted,  in  which  the  courses  are  run  diagonally  to 
the  street  paved.  This  obviated  the  difficulty  for  half  of  the  in- 
tersection^ as  it  brought  that  portion  of  the  traffic  at  right  angles 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


to  the  blocks,  as  shown  by  the  arrows  of  the  figure,  but  for  the 
other  half  of  the  intersection  the  traffic  remained  as  before,  almost 
parallel  with  the  blocks.  Fig.  11  shows  the  method  which  is  in 
use  at  the  present  time,  and  it  is  as  good  an  arrangement  as  can  be 
obtained,  the  principle  being  to  have  the  traffic,  wherever  possi- 
ble, at  right  angles  with  the  blocks,  both  on  the  street  proper  and 
at  intersections. 


Y  \    \ 

\       \       \        \      H 

r  x     x 

_i       \       \       \  •  f- 

B 

FIG.  10. 

The  blocks  generally  should  be  laid  in  courses  square  with  the 
street,  stone  to  stone,  and  all  blocks  in  the  same  course  to  be  of 
uniform  width.  Too  much  care  cannot  be  taken  in  keeping  the 
joints  close,  as  no  matter  how  tight  they  may  seem  to  be  when 
laid,  they  will  always  show  up  more  loosely  after  being  rammed. 

Some  contractors  purchase  their  blocks  by  the  thousand,  others 
by  the  yard.  In  the  former  case  it  is  to  their  interest  to  have  a. 


COBBLE  AND  STONE-BLOCK  PAVEMENTS. 


195 


thousand  blocks  lay  as  many  yards  as  possible,  and  so  there  is  no 
desire  to  keep  the  joints  close,  or  rather  there  is  an  inducement  for 
the  pavement  to  be  made  with  large  and  open  joints.  In  order  to 
prevent  this,  the  specifications  of  Philadelphia  require  that  the 
blocks  shall  be  set  separately,  according  to  their  width,  and  so  that 
the  3J-inch  blocks  shall  lay  32  per  square  yard,  4  rows  to  measure 


FIG.  11. 

16  inches  when  laid;  4-inch  blocks  to  lay  28  per  square  yard,  4 
TOWS  to  measure  18  inches  when  laid;  4|-inch  blocks  to  lay  25  per 
square  yard,  4  rows  to  measure  20  inches  when  laid;  and  they  pro- 
vide that  when  these  conditions  are  not  complied  with  a  reduction 
of  25  per  cent  shall  be  made  from  the  contract  price  for  such  por- 
tion of  the  street  as  does^not  conform  to  the  above  requirements. 
It  would  seem  that  these  restrictions  were  proper  and  justifiable 
if  applied  only  to  the  distance  a  certain  number  of  rows  should 


196        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

measure,  but  where  a  variation  of  4  inches  is  allowed  in  the  length> 
the  number  per  yard  will  vary  according  to  the  length,  and  it  does 
not  seem  as  if  this  variation  is  important. 

After  the  blocks  are  laid  they  should  be  covered  with  a  clean,, 
sharp  sand,  free  from  pebbles,  which  shall  be  swept  or  raked  into 
the  joints  until  they  are  filled;  each  course  should  then  be  set  up 
perpendicular  to  the  surface  of  the  street  with  proper  tools,  and  all 
imperfect  blocks  removed  and  replaced  with  good  ones,  and  then 
the  entire  surface  should  be  thoroughly  rammed.  It  should  then 
be  covered  with  a  second  course  of  sand,  treated  as  before,  and 
rammed  the  second  time.  This  part  of  the  work  should  be  done 
with  great  care.  If  any  soft  spot  or,  as  the  rammer  expresses  it> 
"  soft  blocks  "  are  found,  they  should  be  thoroughly  rammed  until 
they  are  solid  and  then  taken  up  and  the  foundation  brought  to- 
proper  grade  with  added  sand,  and  the  blocks  replaced  and  rammed 
as  before.  Upon  the  proper  ramming  of  the  pavement  depends,  in 
a  great  measure,  how  well  it  will  keep  its  form  and  shape  under 
traffic.  The  entire  surface  of  the  pavement  should  be  covered  with 
one  inch  of  sand  and  allowed  to  remain  under  traffic  a  sufficient 
time  to  permit  all  of  the  joints  to  be  thoroughly  filled. 

Concrete  Foundation. 

With  this  base  the  subgrade  must  be  treated  in  the  same  way 
as  for  sand,  and  the  concrete  then  laid  upon  it.  After  the  concrete 
has  been  completed  and  set  sufficiently  so  that  working  upon  it  will 
do  it  no  harm,  a  cushion  of  sand  should  be  spread  over  the  entira  sur- 
face. The  amount  of  sand-cushion  will  depend  in  a  great  measure 
upon  the  uniformity  of  the  depth  of  the  blocks.  If  the  blocks  are 
of  variable  depths,  the  cushion  must  be  deepened,  as,  on  account  of 
the  irregularities  of  the  concrete  itself,  at  least  1  inch  of  sand 
should  be  allowed  between  the  bottom  of  the  deepest  block  and 
the  concrete. 

When  a  stone-block  pavement  is  laid  upon  a  rigid  base,  the 
joints  between  the  blocks  should  be  filled  with  a  substance  that 
will  make  the  pavement,  as  a  whole,  water-proof.  With  a  sand 
base  this  is  not  desirable  or  necessary,  as,,  whatever  the  joint-filling, 
the  blocks,  being  set  on  sand,  would  always  have  sufficient  moticn 
under  traffic  to  permit  water  to  soak  through;  but  with  a  concrete 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  197 

foundation  a  perfectly  water-tight  pavement  can  easily  be  obtained, 
and  is  desirable  both  from  the  sanitary  and  the  physical  standpoint. 

Joint-filling. 

Portland  Cement. — The  first  filler  that  naturally  suggested 
itself,  in  order  to  make  the  pavement  rigid,  was  a  mixture  of  sand 
and  cement.  This  was  a  mixture  of  one  part  of  sand  and  one  of 
Portland  cement,  and  after  the  blocks  were  rammed  the  joints 
were  poured  full  of  a  grout  made  as  above.  While  making  a  solid 
and  substantial  piece  of  work  at  first,  the  chief  objection  to  this 
filler  is  that  if  for  any  reason  a  joint  becomes  broken  it  always  re- 
mains so,  and  accordingly  it  has  never  been  used  to  any  great 
extent  in  stone  pavements. 

Ferroid.— In  1886  a  filler  called  "ferroid"  was  used  in  Buffalo. 
This  was  made  up  of  10  per  cent  ferroid,  30  per  cent  German  rock 
asphalt,  25  per  cent  Trinidad  pitch,  15  per  cent  coal-tar,  and  20 
per  cent  sand.  The  10  per  cent  ferroid  above  was  supposed  to  be 
composed  of  iron  borings,  sal-ammoniac,  and  sulphur.  This  mix- 
ture was  never  very  extensively  used. 

Murphy  Grout. — Another  joint-filler  used  to  a  considerable  ex- 
tent in  the  West  is  what  is  known  as  "  Murphy's  Grout  Filler."  It 
is  principally  composed  of  iron  slag  and  carbonate  of  lime,  and 
when  used  on  a  street  a  certain  proportion  of  clean,  sharp  sand  is 
added.  This  is  said  to  produce  a  mixture  which  is  as  hard  as  gran- 
ite and  which  attaches  itself  closely  to  the  blocks,  making  them 
solid  and  waterproof. 

Tar  and  Gravel — The  general  custom,  however,  in  granite 
pavements  of  a  concrete  base  is  to  fill  the  joints  with  gravel  and 
paving-cement.  This  paving-cement  in  the  vicinity  of  New  York 
City  is  composed  of  100  Ibs.  of  commercial  No.  4  paving-cement, 
20  Ibs.  refined  asphalt,  and  3  Ibs.  of  residum  oil.  This  commer- 
cial paving-cement  is  made  from  coal-tar.  When  coal  is  distilled 
for  the  purpose  of  making  illuminating-gas,  one  of  the  important 
products  of  the  distillation  is  a  liquid  called  coal-tar.  This  is  a 
very  complex  hydrocarbon,  which  when  further  distilled  produces 
what  is  generally  known  as  pitch.  Its  consistency  and  exact  com- 
position depend  upon  the  amount  of  distillation  to  which  it  has 
been  subjected.  It  is  known  to  the  trade  also  as  paving-cement 
and  numbered  according  to  its  hardness.  It  is  much  like  asphalt 


198        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

in  its  general  appearance,  but  more  brittle.  It  can  be  readily  dis- 
tinguished from  it  by  its  peculiar  odor.  It  is  susceptible  to  heat 
and  cold,,  cracking  in  winter  and  becoming  soft  in  summer  at  a 
temperature  which  would  not  affect  asphalt.  For  this  reason  it  is 
necessary  in  using  it  on  streets  to  flux  it  with  a  certain  amount  of 
asphalt. 

Granite  blocks  on  a  concrete  base  are  not  laid  with  close  joints. 
The  idea  is  not  to  fill  the  joints  entirely  with  paving-cement, 
but  leave  them  sufficiently  open  so  that  they  can  be  filled  with 
gravel  and  then  the  interstices  in  the  gravel  filled  with  a  paving- 
cement  which  forms  a  perfectly  tight  joint  and  one  which,  if  broken 
during  the  cold  weather,  will  soften  and  become  perfect  again  at  a 
higher  temperature.  The  joints  should  be  left  just  wide  enough 
to  allow  them  to  be  filled  with  a  gravel  which  will  permit  the  pitch 
to  flow  easily  through  the  interstices  and  thus  make  a  solid  joint. 
A  joint  |  of  an  inch  wide  after  the  blocks  are  rammed  is  sufficient 
to  accomplish  this  purpose. 

Gravel  for  such  a  joint  should  be  screened  so  that  it  will  all  be 
retained  in  a  screen  having  J-inch  mesh,  and  will  pass  a  screen  of 
•J-inch  mesh.  If  the  gravel  be  finer  and  allowed  to  grade  down  to 
coarse  sand,  it  will  not  allow  a  free  flowing  of  the  cement,  and  the 
lower  part  of  the  joint  will  not  be  filled.  The  pavement  should  be 
laid  practically  in  the  same  manner  as  described  for  the  sand  base 
except  as  to  width  of  joints  and  the  ramming,  there  being  so  small 
an  amount  of  sand  under  the  blocks  that  much  ramming  is  not 
needed  on  a  concrete  base.  In  all  block  pavements  special  care 
should  be  taken  to  break  the  joints  with  a  lap  of  at  least  3  inches, 
and  preferably  in  the  centre  of  the  block.  Where  the  blocks  run 
of  uneven  length,  the  inspector  will  have  to  watch  pretty  carefully 
to  see  that  this  is  accomplished.  After  the  blocks  have  been  laid, 
the  gravel,  which  has  been  heated  to  a  temperature  that  will  posi- 
tively insure  its  being  perfectly  dry,  should  be  spread  over  the  sur- 
face and  into  the  joints  in  such  an  amount  that  when  the  blocks 
are  rammed  the  joints  shall  be  filled  within  3  inches  of  the  top. 
The  paving-cement  should  be  poured  into  the  joints  until  they  are 
full  to  the  top  of  the  gravel  and  until  it  ceases  to  run  off.  The 
joints  should  then  be  filled  to  the  top  with  more  gravel  heated  to 
a  temperature  of  not  less  than  200  degrees,  when  the  joints  should 
be  again  poured  with  the  paving-cement  until  they  are  entirely 


COBBLE  AND  STONE-BLOCK  PAVEMENTS. 


199 


filled  and  flush  with  the  surface  of  the  pavement.  This  part  of  the 
work  should  closely  follow  that  of  the  pavers,  so  that  when  the 
pavers  stop  work  for  the  day,  the  rammers  and  cement-pourers  will 
require  but  little  time  to  complete  the  pavement  that  is  laid.  If 
the  gravel,  after  the  joints  are  filled,  becomes  wet,  it  will  not 
properly  receive  the  cement,  as  any  appreciable  amount  of  water 
always  causes  it  to  foam  and  not  form  a  solid  joint.  When  treated 
in  this  manner,  a  yard  of  pavement  will  require  about  1^  cubic 
feet  of  gravel  and  3£  gallons  of  paving-cement  for  joint-filling. 
Fig.  12  represents  a  section  of  granite  block  pavement  on  a  con- 
crete base. 


It" 


FIG.  12. 

Before  proceeding  with  the  construction  of  the  base,  the  cross- 
section  of  the  street  must  be  determined.  This  is  a  question  that 
has  been  discussed  at  considerable  length  by  engineers  and  upon 
which  there  is  quite  a  difference  in  opinion.  The  best  form  of  the 
street  for  traffic  alone  would  be  a  straight  line  from  one  gutter  to 
another,  but  this  would  allow  the  water  during  any  storm  to  spread 
out  over  the  entire  street,  making  it  difficult  for  pedestrians  to 
Across,  and  also,  in  case  of  any  settlement  of  the  pavement,  holes 
would  be  more  easily  formed. 

The  early  pavements  in  this  country  had  gutters  in  the  centre, 
and  all  the  water  was  therefore  led  to  this  portion  of  the  street. 
By  this  arrangement  the  most  valuable  part  of  the  street  was  prac- 
tically given  up  to  drainage,  and  the  water  was  delivered  to  the 
intersecting  street  at  the  centre,  where  it  was  difficult  to  take  care 
of  it.  The  remedy  for  this  was  to  make  the  surface  of  the  street 
convex  instead  of  concave,  and  just  how  much  convexity  should 
be  given  is  a  question  for  discussion.  The  object  of  the  crown  in 
the  street  is  twofold:  first,  to  give  sufficient  slope  to  the  pavement 
to  carry  the  water  quickly  from  the  centre  to  the  gutter;  and 
second,  to  confine  the  water,  in  the  case  of  storms,  to  as  small  a 


200        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

portion  of  the  street  as  possible,  so  as  not  to  interfere  with  pedes- 
trian travel.  When  a  street  is  first  being  paved,  and  nt>  permanent 
improvements  of  any  character  have  been  constructed,  the  problem 
of  the  cross-section  is  comparatively  simple.  It  only  remains  to 
adopt  a  standard  depth  of  gutter  and  a  standard  crown,  and  noth- 
ing will  interfere  with  carrying  it  out.  When,  however,  the  street 
is  being  repaved  and  has  permanent  sidewalks,  so  that  the  elevation 
of  the  old  curbs  can  be  changed  but  little  if  any,  and  one  curb  is 
a  considerable  elevation  above  the  other,  the  problem  is  different. 

A  pavement  should  be  laid  with  its  general  ^surface  as  nearly 
uniform  as  possible,  and  with  but  little  slope  from  one  side  to  the 
other.  When,  however,  the  difference  in  the  elevation  of  the  curbs 
is  great,  by  making  different  depths  of  gutter  this  trouble  can  be 
very  materially  helped. 

Two  principles  govern  in  determining  the  depths  of  gutters. 
First,  they  should  not  be  made  so  deep  as  to  present  a  high  step- 
for  pedestrians,  nor  so  shallow  as  to  present  little  obstruction  to 
wheeled  vehicles  and  to  have  little  water  capacity.  Unless  for  some: 
special  reason,  the  gutter  should  not  be  deeper  than  9  nor  less  than 
4  inches.  By  thus  making  the  gutter  on  the  high  side  of  the  street 
9  inches  deep,  and  on  the  low  side  4  inches,  the  difference  of  5 
inches  is  overcome  at  once,  so  that  with  a  difference  of  elevation 
not  greater  than  5  inches  the  crown  of  the  pavement  can  be  put 
in  the  centre  and  the  two  sides  will  be  symmetrical.  If,  however,, 
there  be  a  greater  difference  than  5  inches,  the  crown  can  generally 
be  left  in  the  centre,  with  an  increased  difference  of  3  or  4  inches,, 
leaving  the  street  with  a  greater  slope  on  one  side  than  the  other. 

When  the  difference  becomes  so  great  that  the  upper  side  of 
the  street  is  nearly  flat,  and  the  lower  side  correspondingly  steep,, 
the  difference  can  be  overcome  to  a  certain  extent  by  changing  the 
crown  from  the  centre  to  the  upper  quarter  of  the  street.  By  giv- 
ing the  crown  an  arbitrary  elevation  of  2  or  3  inches,  as  may  be 
necessary  to  insure  some  fall  from  the  crown  to  the  high  gutter,, 
the  least  possible  fall  from  the  crown  to  the  lower  gutter  will  be 
obtained,  and  the  result  is  a  surface  -that  is  a  compound  curve,  with 
the  lower  three-quarters  of  one  radius  and  the  upper  one-quarter 
of  another,  not  necessarily  tangent,  but  so  near  it  that  the  difference: 
can  never  be  discovered  by  the  e}re. 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  i^Ol 

When,  however,  street-car  tracks  are  laid,  or  to  be  laid,  on  a 
street,  the  problem  presents  a  different  phase.  While  it  is  not 
necessary  that  both  tracks  should  be  at  the  same  elevation,  it  is 
necessary  that  the  two  rails  on  the  same  track  should  be  level; 
therefore  it  is  not  possible  to  fit  a  track  to  a  curved  surface.  When 
there  is  a  material  difference  between  the  two  curbs,  the  track  OH 
the  lower  side  can  be  set  at  the  maximum  difference  of  3  inches 
below  the  upper.  Then  by  making  the  high  gutter  the  maximum 
depth  and  the  low  gutter  the  minimum,  the  best  possible  result 
is  obtained.  Possibly,  however,  in  doing  this  it  may  be  neces- 
sary to  run  the  water  from  the  gutter  to  the  centre  rather  than 
from  the  track  to  the  gutter.  While  this  is  not  desirable,  it  is  not 
positively  bad,  and,  under  circumstances  similar  to  the  above,  quite 
often  must  be  done.  If  the  longitudinal  grade  is  considerable  and 
the  distance  from  the  car-track  to  the  gutter  small,  there  is  no  par- 
ticular objection  to  making  the  pavement  level  or  on  a  straight  line 
from  the  track  to  the  gutter.  When  such  an  arrangement  is  nec- 
essary, the  result  is  often  the  draining  of  quite  a  considerable 
surface  to  the  tracks  where  the  water  runs  down  to  the  first  inter- 
section, and  at  that  point  a  catch-basin  should  be  provided  between 
the  tracks  to  take  care  of  it. 

Crown. 

Very  few  engineers  agree  as  to  the  exact  amount  of  crown  to  be 
given  to  a  street,  and  it  is  also  varied  according  to  the  material. 
Some  engineers  vary  the  crown  with  the  longitudinal  grade,  having 
a  formula  by  which  the  crown  can  be  calculated  with  the  different 
grades.  This,  however,  does  not  seem  to  be  necessary.  Any  crown 
at  all  is  a  modification  of  the  best  cross-section  of  the  street  for 
traffic  designed  simply  for  the  purpose  of  drainage.  If  then  a  light 
crown  will  drain  the  street  to  the  gutter,  the  minimum  amount 
can  be  used  in  almost  every  case,  and  there  seems  to  be  no  necessity 
for  running  the  amount  above  the  minimum  unless  it  is  positively 
required,  when  it  is  remembered  that  the  nearer  flat  a  pavement  is 
the  more  truly  it  will  serve  traffic,  which  is  its  true  province. 

Assuming  the  roadway  of  the  street  to  be  30  feet  wdde,  and 
adopting  a  crown  of  4  inches,  which  does  not  inconvenience  travel, 
a  fall  towards  the  gutter  of  the  central  J/3  will  be  4/9  of  an  inch,  or 


202        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 


at  the  rate  of  9  inches  per  100  feet,  which  is  sufficient  for  drainage. 
The  fall  of  the  second  1/3  towards  the  gutter  is  !1/3  inches,  or  at 
the  rate  of  27  inches  per  100  feet,  while  that  of  the  1/3  adjacent 
to  the  curb  is  22/9  inches,  or  at  the  rate  of  44  inches  per  100  feet. 
Table  No.  59  gives  the  fall  from  the  centre  to  the  gutter  of  each 
third  of  the  roadway,  with  different  widths  and  of  different  crowns. 

TABLE  No.  59. 


Fall 

Fall 

Fall  to 

Width 
of 
Roadway. 

s_ 

Crown. 

towards 
Gutter  in 
Central 
Uof 
Roadway. 

Rate 
per  100. 

towards 
Gutter  in 
Second 

Kof 

Roadway. 

Rate 
per  100. 

Gutter 
in  fc  of 
Roadway 
adjacent 
to  Curb. 

Rate 

per  100. 

24  feet 

3  inches 

*  inch 

Scinches 

1  inch 

2  ft.  1  in. 

If  inches 

3  ft.  6  in. 

30      ' 

4    " 

i   ;; 

9      < 

1*  inches 

2        3    ' 

2f 

3    '   8    ' 

30      ' 

6     " 

13*     ' 

2       " 

3        4    ' 

3| 

5    '  6    ' 

3:3      ' 

5     " 

f      " 

9±     ' 

If     " 

2        4    ' 

3    '   3    ; 

43      ' 

6     " 

f     " 

8*     ' 

2      " 

2        1     ' 

3* 

3    '   6    ' 

GO      ' 

8     " 

1     " 

8f  '  ' 

2*     " 

2        3    ' 

4f 

3    '   9    ' 

This  table  shows  ver)r  plainly  that  even  on  a  level  grade  the 
water  will  drain  readily  from  the  centre  to  the  gutters,  and  at  the 
same  time  the  roadway  will  be  such  as  to  be  very  favorable  for 
travel.  Under  the  heading  of  Thirty-foot  Eoadways,  figures  are 
given  for  the  6-inch  crown  as  well  as  4-inch,  showing  how  very 
materially  the  side  slope  increases  with  the  crown,  and  this  side 
slope,  in  slippery  weather,  is  much  more  damaging  to  horses  than 
a  straight  horizontal  slope. 

These  figures  are  recommended  as  the  proper  crown  on  all  Level 
streets  of  improved  pavements,  except  the  6-inch  crown  on  a  thirty- 
foot  roadway.  The  curve  of  the  pavement  is  in  reality  a  parabola, 
but  in  the  distance  used  is  practically  a  circle.  It  can  be  best  laid 
out  on  the  crown  by  stretching  a  line  from  curb  to  curb,  and  meas- 
uring the  ordinates  down  from  the  line  at  any  desired  interval 
according  to  the  width  of  the  street.  The  length  of  the  ordinate 
can  be  determined  by  the  simple  formula 


in  which  D  is  equal  to  the  distance  from  the  centre  to  any  point 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  203 

in  feet,  #  equals  |  the  width  of  roadway,  C  equals  the  crown  in 
inches,  and  0  equals  the  ordinate  in  inches. 

When  a  street  has  been  laid  out  in  this  way  and  the  foundation 
rolled  and  prepared  as  heretofore  described,  the  next  work  is  to 
lay  the  concrete;  and  in  order  to  insure  the  concrete  being  laid  of 
the  proper  thickness,  rows  of  stakes  some  10  feet  apart  longitudi- 
nally should  be  set  across  the  street  at  intervals  of  6  or  8  feet, 
according  to  the  width  of  the  roadway,  and  driven  to  such  depth 
that  the  tops  will  be  on  the  same  level  as  that  required  for  the  con- 
crete, the  proper  elevation  for  the  stakes  being  determined  by  meas- 
uring down  from  the  line  in  the  same  manner  as  for  the  subgrade. 

Concrete. 

According  to  Table  No.  25  it  is  seen  that  it  requires  2.79 
barrels  of  cement  and  21  cubic  feet  of  sand  to  make  1  cubic  yard 
of  mortar.  Ordinary  broken  stone  of  uniform  size  contains  about 
50  per  cent  voids,  but  no  commercial  broken  stone  is  uniform,  as  it 
is  more  or  less  graduated  in  size,  so  that  the  voids  are  generally 
only  45  per  cent.  Assuming,  then,  that  the  broken  stone  contains 
45  per  cent  voids,  and  adding  50  per  cent  of  mortar  so  as  to  insure 
a  complete  filling  of  the  voids,  1  cubic  yard  of  mortar  mixed  with 
2  cubic  yards  of  stone  will  make  56.7  cubic  feet  or  2.1  cubic  yards 
of  concrete,  and  the  amount  of  material  necessary  for  1  cubic  yard 
of  concrete  is  1.33  barrels  of  cement,  25.7  cubic  feet  of  stone,  and 
10  cubic  feet  of  sand. 

In  mixing  the  concrete,  if  it  is  done  by  hand,  platforms  will  bo 
required  for  the  mixing,  some  10  feet  square,  and  for  an  economical 
organization  two  boards  should  be  worked  together.  The  proper 
organization  would  be:  one  foreman  and  four  mixers  for  each  board, 
four  wheelers,  one  rammer,  and  one  man  to  carry  cement  and  sup- 
ply water.  Eight  wheelbarrows  will  be  required.  Enough  cement 
should  be  mixed  in  one  batch  to  fill  two  wheelbarrows,  which  will 
be  not  far  from  one  barrel,  but  as  cement  is  generally  delivered  in 
sacks,  it  can  be  easily  regulated. 

Assuming  that  the  concrete  is  to  be  mixed  in  the  proportion  of 
one  part  cement,  two  parts  sand,  and  four  parts  broken  stone,  the 
m  en  with  the  wheelbarrows  should  wheel  four  barrows  of  sand  upon 
the  first  board,  and  the  cement  should  be  added.  The  barrowme'n 


204        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

should  immediately  go  to  the  stone-pile  and  wheel  up  four  barrows 
of  stone,  leaving  it  standing  by  this  board  on  the  barrows,  return- 
ing again  for  the  other  four  barrows  of  stone,  and  by  the  time  they 
have  reached  the  b^ard  the  mixers  should  have  the  sand  and  cement 
thoroughly  incorporated  into  the  mortar,  when  the  barrows  of 
stone  should  be  dumped  on  the  board  of  mortar  and  then  mixed  as 
described  in  a  previous  chapter.  The  barrowmen  should  then 
proceed  in  the  same  manner  to  the  other  board,  and  by  the  time 
they  have  furnished  it  with  sand  and  stone,  the  mixers  on  the  first 
board  should  have  the  concrete  mixed  and  placed  on  the  street, 
when  the  operation  should  be  repeated  and  continued  throughout 
the  day.  When  hand-work  is  done,  the  boards  should  be  situated 
so  near  the  concrete  that  the  mixers  can  shovel  direct  from  the 
board  to  the  face  of  the  concrete,  when  the  rammers  should  grade 
and  ram  it  thoroughly  until  the  mortar  flushes  to  the  surface  and 
no  longer.  For  this  work  the  expense  for  material  would  be: 

1.33  bbls.  of  cement  at  90  cts $1.20 

.95  cubic  yards  broken  stone  at  $1.25 1.19 

.37  cubic  yards  sand  at  $1.00 37 

Total  per  cubic  yard  for  material $2.76 

Or  per  square  yard,  6  inches  deep,  46  cents. 

FOB   LABOR. 

1    foreman $3.00 

14  laborers  at  $1.25 17.50 

Total $20.50 

This  organization  should  lay  240  square  yards  per  day,  which 
at  the  above  figures  would  amount  to  8.6  cents  per  square  yard, 
ir.aking  a  total  of  54.6  cents  per  square  yard  for  hand-mixed  con- 
crete. 

If,  however,  the  machine  described  on  page  129  and  shown  in 
Fig.  2  be  used,  the  organization  and  results  are  very  different.  An 
engineer  would  be  required  to  run  the  engine,  and  a  pair  of  horses 
to  draw  the  mixer  along  as  the  work  progresses.  Men  are  required 
fop-  setting  grade-pegs  as  before,  shovelling  material  into  the  ma- 
chine and  wheeling  it  to  the  work,  and  as  it  is  dumped  from  the 
-wheelbarrows  into  piles  it  requires  to  be  raked  and  graded  by 
laborers  for  that  purpose  in  addition  to  the  rammers  used  for  hand- 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  205 

work,  so  that  a  total  of  30  laborers  is  required  for  the  organization, 
— making  the  complete  outfit: 

1  foreman $  3.00 

1  engineer 3.00 

1  pair  horses 3.50 

Fuel  and  water t 2.00 

30  laborers  at  $1.25..  37.50 


Total $49.00 

This  gang  should  lay  per  day  800  square  yards  of  concrete  6 
inches  thick,  at  a  cost  of  6.1  cents  per  square  yard. 

After  the  concrete  is  laid,  if  the  weather  be  warm,  it  should  be 
immediately  covered  with  a  cushion  of  sand,  and  with  ordinary 
cement  the  pavement  can  be  laid  in  from  two  to  three  days  after- 
wards, in  accordance  with  the  method  heretofore  described.  The 
particular  things  which  an  inspector  should  watch  on  a  pavement 
with  tar  and  gravel  joints  are  that  the  joints  are  not  filled  too  nearly 
full  with  the  gravel,  and  also  that  the  gravel  is  so  ^nearly  uniform 
in  size  that  it  will  permit  the  paving-cement  to  flow  freely  through 
it.  If  the  joints  be  filled  pretty  nearly  to  the  top,  and  the  gravel 
contains  any  appreciable  amount  of  sand,  the  paving-cement,  in- 
stead of  running  to  the  bottom  of  the  joint,  will  flow  into  the  gravel 
but  a  very  short  distance,  and  while  seeming  to  be  full,  the  joint 
contains  in  reality  a  very  small  amount  of  the  cement.  In  order, 
too,  that  the  cement  should  flow  freely,  it  should  be  heated  to  a 
temperature  of  not  less  than  300  degrees  when  poured.  It  should 
l>e  heated  in  kettles  brought  as  nearly  to  the  work  as  possible,  so 
that  it  will  not  be  cooled  in  being  carried  to  the  work,  and  that  the 
process  of  pouring  may  be  done  as  expeditiously  as  possible.  For 
work  of  this  character  there  will  be  required  per  square  yard  of 
pavement  3|  gallons  of  paving-cement,  1J  cubit  feet  of  gravel,  and 
1J  cubic  feet  of  sand.  The  organization  of  the  gang  on  a  piece  of 
work  that  was  carried  out  recently  was: 

10  payers      at  $4  50  per  day $45.00 

5  rammers  "      3.50     "      "    17.50 

6  chuckers  "      1.50    "      "    9.00 

20  laborers    "      1.25    "     "    25.00 

Total..  .   $96.50 


206        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

This  gang  laid  on  an  average  650  yards  per  day  on  a  street  44 
feet  wide,  and  it  required  22%  blocks,  according  to  the  New  York 
specifications  in  Table  No.  57,  per  square  yard,  so  that  the  cost 
for  material  would  be: 

22£  blocks  at  5£  cts.  each $1.24 

3£  gallons  paving-cement  at  7  cts 24£ 

1J  cubic  feet  gravel  at  $1.95  per  cubic  yard 09f 

li  cubic  feet  of  sand  at  $1.00  per  cubic  yard 06 

1  square  yard  of  concrete 55 

Labor  as  above 15 


Total    $2.34i 

For  a  granite  pavement  on  sand  the  organization  would  be: 

4  pavers  at  $4.50  per  day $18.00 

2  rammers  "      3.50     "      "    7.00 

3  chuckers  "      1.50    "      "    4.50 

3  laborers  "      1.25     "  "    .                                      3.75 


Total $33.25 

This  organization  laid  280  square  yards  per  day  on  a  street  30 
feet  wide  free  from  street-car  tracks,  at  a  cost  of  12  cents  per  square 
yard  for  labor.  On  another  street  where  there  were  street-car  tracks 
the  pavers  averaged  63  yards  per  day  instead  of  70  as  above. 

Assuming,  then,  the  sand  foundation  to  be  of  such  depth  as  ta 
require  1  cubic  yard  for  5  square  yards  of  pavement,  and  that  24 
blocks  will  lay  a  square  yard  of  pavement,  the  material  would  cost: 

24  blocks  at  5J  cts $1.32 

.20  cubic  yards  of  sand  at  $1 20 

Labor   12 

Total  on  a  sand  base $1.64 

In  all  estimates  of  cost  of  work,  no  special  pains  have  been  taken 
to  get  the  exact  cost  of  material,  as  that  must  vary  very  materially 
with  each  locality,  but  the  figures  used  are  approximately  correct 
for  New  York  City  in  1899.  The  amount  of  material  required, 
however,  and  the  amount  of  work  done,  are  in  almost  every  case  the 
result  of  actual  observation. 


COBBLE  AND  STONE-BLOCK  PAVEMENTS.  207 

Medina  Sandstone. 

The  city  of  Cleveland,  Ohio,  has  probably  more,  if  not  better, 
pavements  of  Medina  sandstone  than  any  other  city  in  the  country. 
It  is  the  only  stone  pavement  in  use  there  at  the  present  time,  and 
gives  almost  perfect  satisfaction.  It  is  said  by  the  City  Engineer 
to  have  a  life  of  25  years,  which  is  all  that  can  be  asked  of  granite. 
The  pavement  is  laid  on  concrete  in  a  very  careful  and  thorough 
manner,  the  blocks  being  made  so  as  to  be  smooth  and  even. 

After  describing  the  dimension  and  form  of  blocks  the  Cleve- 
land specifications  say:  "  The  paving-blocks  as  here  referred  to 
shall  be  understood  to  mean  blocks  of  Medina  sandstone,  prepared 
in  the  proper  manner  for  dressed-block  paving,  by  nicking  and 
breaking  the  stones  from  larger  blocks  as  is  done  in  the  quarries 
where  such  blocks  are  usually  prepared,  and  not  made  by  redressing 
and  selecting  from  common  stone  paving  material.  The  stone  to 
be  flat  and  even  at  bottom,  which  shall  be  parallel  to  the  top- sur- 
face, with  both  top  and  bottom  of  stone  at  right  angles  at  least  at 
one  end  of  the  stone,  so  as  to  set  squarely  and  firmly  in  space  with- 
out the  use  of  a  paving-hammer." 

While  the  dimensions  of  the  stone  in  thickness  range  from  3J 
to  5  inches,  the  blocks  are  divided  into  three  classes,  the  1st  class 
including  blocks  from  3J  to  3J  inches,  and  the  2d  class  blocks 
from  3}  to  and  including  4J  inches.  Class  No.  3  embraces  blocks 
from  4£  to  and  including  5  inches.  Blocks  in  class  No.  1  are  to 
be  marked  with  red  paint,  blocks  in  class  No.  2  with  blue  paint, 
and  those  in  class  No.  3  with  black  paint,  so  that  when  the  blocks 
are  delivered  on  the  street  each  class  can  be  easily  recognized  and 
laid  by  themselves  in  the  pavement.  Instead  of  being  set  with 
open  joints  as  is  the  case  with  granite  on  concrete,  with  tar  and 
gravel  joints,  these  stones  in  Cleveland  are  set  tight  together  with- 
out any  gravel  or  sand  being  placed  on  the  top.  Upon  the  com- 
pletion of  every  course,  if  necessary,  the  blocks  are  driven  together 
and  the  course  straightened  by  the  use  of  a  heavy  sledge  and  wood 
block  placed  against  the  stone  so  as  to  insure  close  work  and  a 
straight  course  across  the  street. 

The  blocks  are  rammed  three  separate  times  with  a  wooden 
rammer  weighing  not  less  than  80  Ibs.,  and  the  surface  brought  up 


90S        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

to  the  proper  grade  by  the  use  of  a  long  straight-edge.  The 
pavement  is  also  rolled  when  necessary  to  bring  it  to  a  true  sur- 
face. After  ramming  and  rolling,  or  even  during  the  process,  the 
pavement  is  sprinkled  or  washed  with  water  so  as  to  free  the  joints 
to  their  full  depth  from  sand  and  thoroughly  bed  them  in  the  sand- 
cushion.  The  spaces  between  the  blocks  are  then  filled  \vith  a 
composition  consisting  of  asphaltic  cement,  Pordand-cement  filler, 
Murphy  grout,  or  such  other  filling  as  may  be. ordered.  The  asphalt 
filler  consists  of  10  per  cent  of  refined  Trinidad  asphalt,  mixed 
with  coal-tar  cement,  distilled  at  a  temperature  of  not  less  than 
600  degrees,  and  the  whole  mixed  with  such  proportion  of  still  wax 
as  will  prevent  it  from  being  too  soft  in  warm  weather  or  too  brittle 
in  cold.  It  is  used  at  a  temperature  of  not  less  than  300  degrees. 

Portland-cement  filler  is  made  of  equal  parts  of  the  best  Port- 
land cement  and  clean,  sharp  Lake  sand,  mixed  with  a  sufficient 
amount  of  water  to  permit  it  to  flow  freely  into  the  joints.  The 
grouting  is  done  by  two  applications,  the  lower  one-third  of  the 
joint  being  filled  with  a  somewhat  thinner  grout  than  for  the  re- 
maining two-thirds.  The  upper  space  is  filled  with  a  thicker 
grout,  and  refilled  if  necessary,  until  the  joints  all  remain  full. 
This  pavement  is  generally  allowed  to  stand  one  week  before  being 
used.  The  entire  surface  of  the  pavement  when  completed  is  cov- 
ered with  a  -J-inch  coating  of  clean  sand.  The  cost  of  this  pave- 
ment in  Cleveland  is  about  $3.25  per  square  yard. 

The  Medina  sandstone  pavements  of  Rochester,  N".  Y.,  are  laid 
in  about  the  same  way  as  those  of  Cleveland  and  under  very  nearly 
the  same  general  specifications,  except  that  they  do  not  call  for  the 
blocks  to  be  divided  into  classes  according  to  width,  and  the  blocks 
are  laid  with  J-inch  joints  instead  of  being  laid  stone  to  stone,  and 
these  joints  are  filled  with  gravel  into  which,  is  poured  hot  paving- 
cement  until  the  joints  are  filled.  Rochester  pavements  of  this 
character  have  cost  on  the  average  $2.54  per  square  yard. 

Cross-walks. 

At  each  intersection  in  stone  pavements,  cross-walks  must  be 
laid  to  accommodate  pedestrian  travel.  It  has  been  customary  in 
New  York  to  lay  cross-walks  of  Hudson  River  bluestone  in  all  cob- 


f" 

COBBLE  AND  STONE-BLOCK  PAVEMENTS.  209 

ble  and  Belgian  pavements,  and  granite  cross-walks  where  the 
streets  are  paved  with  granite.  In  the  West,  where  sandstone  is 
used  for  paving,  the  cross-walks  are  made  of  the  same  material. 
'The  bluestone  cross-walks  in  New  York  consist  of  two  courses  of 
Hudson  River  bluestone  2  feet  wide  and  from  6  to  8  inches  thick, 
separated  by  one  course  of  granite  or  Belgian  blocks,  their  length 
being  not  less  than  -i  nor  more  than  6  feet.  The  granite  cross- 
walks as  at  present  used  in  New  York  are  not  less  than  4  nor  more 
than  6  feet  in  length,  1J  feet  wide,  and  not  less  than  6  nor  more 
than  8  inches  thick  throughout.  Cross-walks  were  originally  laid 
with  the  end  joints  parallel  to  the  line  of  the  street,  as  shown  at 
A,  Fig.  9.  This  gives  a  joint  18  inches  or  2  feet  in  length,  accord- 
ing to  the  kind  of  stone,  parallel  to  the  traffic.  In  a  few  years 
these  joints  always  wear  badly,  so  that  a  rut  is  formed,  especially, 
as  is  often  the  case,  if  the  joint  was  not  squared  to  its  full  depth. 
To  obviate  this  the  joints  were  cut  diagonally  with  a  slope  of  about 
6  inches  in  the  width  of  the  stone,  so  that  no  traffic  would  be  par- 
allel to  the  joint.  At  first  they  were  all  as  shown  at  B  in  Fig.  10, 
but,  as  in  the  case  of  the  blocks  laid  on  the  intersection,  this  was 
objectionable,  as  it  made  the  joints  parallel  to  the  traffic  turning 
the  corner.  The  proper  way  is  to  lay  them  as  shown  at  C  and  D 
in  Fig.  11,  with  a  keystone  in  the  centre,  so  that  the  joint  is  al- 
ways opposed  to  the  traffic. 

It  is  customary  in  most  cities  to  construct  sewers  with  catch- 
basins  for  storm-wat:  r  at  the  curb-corners  of  the  intersections.  This 
makes  it  necessary  to  carry  the  water  over  the  cross-walk,  and  if 
there  is  an  appreciable  step  from  the  pavement  to  the  curb,  it  is 
better  to  stop  the  cross-walk  within  about  6  inches  of  the  curb  and 
depress  the  blocks  in  the  intervening  space  so  that  the  water  can 
run  down  the  gutter  at  the  end  of  the  crossing,  unless  the  fall  be 
too  great.  A  much  better  arrangement,  however,  can  be  had  if, 
instead  of  one  basin  at  the  corner,  two  smaller  basins  could  be  put 
oack  of  the  cross-walk,  as  shown  at  E  and  F,  Fig.  11.  This  would 
allow  the  intersection  to  be  paved  almost  to  a  level  with  the  curb, 
and  so  that  the  street  would  present  practically  no  obstruction  to 
pedestrian  travel.  When  it  is  considered  how  much  money  is  ex- 
pended in  the  paving  of  a  street  in  order  to  make  it  convenient 
for  the  public,  it  would  seem  that  the  little  extra  expense  neces- 


210        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

sary  for  this  improvement  would  be  justified  when  the  results 
obtained  are  considered. 

Granite  Pavement  in  Vienna. 

Cubes  are  mostly  employed  measuring  7J  inches.  On  streets 
having  a  grade  of  1  in  50  the  blocks  are  laid  at  an  angle  of  45°  to 
the  line  of  the  street.  On  grades  up  to  1  in  40  they  are  laid  at  right 
angles  to  the  street  line.  If  the  grade  is  more  than  1  in  40,  cubes 
measuring  about  5£  inches  are  used,  also  set  at  right  angles  to  the 
street.  But  if  the  grade  is  more  than  1  in  33,  the  smaller  blocks 
are  grooved  to  provide  a  foothold  for  horses.  The  blocks  are  laid 
on  a  foundation  of  6  inches  of  gravel,  upon  which  is  a  sand-cushion 
of  1J  inches. 

Generally  the  joints  are  filled  with  sand,  but  on  heavy  traffic 
arid  built-up  streets  an  asphalt  filler  is  used  for  the  joints.  This 
asphalt  filler  increases  the  cost  about  30  cents  per  square  yard.  The 
average  price  of  the  pavement  is  from  $2.60  to  $3  per  yard. 


CHAPTER    VIII. 

ASPHALT    PAVEMENTS. 

THE  early  history  of  asphalt  pavements  in  Europe  was  pretty 
generally  given  in  the  chapter  on  the  history  of  pavements. 

In  the  United  States,  previous  to  1866,  sidewalks  and  cross- 
walks had  been  laid  in  Lock  Haven,  Pa.,  of  coal-tar  mixed  with 
gravel,  broken  stone,  coal-ashes,  etc.,  under  a  special  patent  issued 
to  a  Mr.  Scrimshaw,  from  whom  the  name  of  the  pavement  was  de- 
rived. In  1867  a  small  portion  of  the  roadway  of  one  of  the  drives 
in  Prospect  Park,  Brooklyn,  was  paved  with  the  same  material.  So 
successful  was  that  experiment  that  the  following  year  a  similar 
pavement  was  laid  on  Diamond  Street,  now  Lenox  Road,  Flatbush, 
L.  I.  The  foundation  consisted  of  a  course  of  2-inch  broken  stone 
5  inches  thick,  mixed  with  sand,  coal-ashes,  and  tar.  The  wearing 
surface  was  similar  to  the  foundation,  except  that  no  stone  was  used 
greater  than  1  inch  in  any  dimension.  This  made  a  pavement  that 
lasted  for  more  than  twenty  years,  and  when  the  street  was  repaved 
in  1896  some  of  it  was  found  intact  and  served  as  a  foundation  for 
the  new  asphalt  pavement.  This  street  was  probably  the  first  one 
regularly  paved  with  a  bituminous  material  in  the  United  States. 

Such  pavements  gave  good  satisfaction'  as  long  as  a  good  quality 
of  tar  could  be  obtained,  but  on  account  of  the  large  amount  of 
volatile  oils  contained  in  the  tar  it  was  necessary  to  close  a  street 
to  travel  for  about  thirty  days  after  its  completion,  and  with  some 
tars  fifty  and  even  sixty  days.  This  was  objectionable,  and  the 
difficulty  was  obviated  in  1871  by  a  combination  of  roofing-pitch 
and  creosote,  or  dead  oil,  which  combination  was  patented  in  March 
of  that  year  by  a  Mr.  B.  Abbott.  With  this  material  a  better  pave- 
ment was  laid,  and  one  that  could  be  used  the  following  day.  This 
was  known  as  the  Abbott  patent.  Streets  were  paved  under  this 

211 


212        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

patent  in  Brooklyn  and  Washington  which  were  in  good  condition* 
for  fourteen  or  fifteen  years.  Some  of  the  old  Brooklyn  pavements, 
are  found  even  now  when  some  of  the  older  asphalt  pavements  are 
"being  relaid.  As  coal-tar  pavements  failed,  asphalt  was  laid  over 
the  tar  as  a  foundation 

In  1878  Delaware  Avenue,  Buffalo,  was  paved  with  Trinidad 
asphalt,  fluxed  with  still  wax,  or  wax  tailings.  This  still  wax  was  a 
waxy  oil,  dark  green  in  color,  being  the  last  product  of  the  distilla- 
tion of  petroleum  before  coke  is  reached,  and  was  free  from  all  oils 
that  would  be  driven  off  at  a  temperature  of  less  than  600  degrees. 
According  to  the  report  of  the  Board  of  Public  Works  in  Buffalo,, 
this  street  cost  for  repairs  a  total  amount  of  $515  until  it  was  re- 
laid  in  1892. 

In  the  Delaware  Avenue  pavement  sand  was  not  used  for  a. 
matrix,  but  instead  a  hard  broken  stone,  screened  to  exclude  all 
above  \  inch  in  size  and  to  permit  smaller  stones  even  down  to- 
dust.  Before  long,  however,  chemical  research  had  discovered 
other  and  more  valuable  uses  for  the  wax,  and  it  became  too  ex- 
pensive for  street  use,  and  recourse  was  had  to  residuum  oil. 

In  the  mean  time  coal-tar  streets  of  different  mixtures  had  been, 
laid  in  Washington  soon  after  1870.  They  were  laid  under  a  good 
many  different  patents,  of  as  many  different  mixtures,  receiving 
their  name  generally  from  that  of  the  patentee.  The  base  was  gen- 
erally made  up  of  broken  stone  4  to  6  inches  thick,  cemented  to- 
gether  with  coal-tar  and  covered  with  a  binder  coat  about  1  inch 
thick  composed  of  pebbles,  fine  broken  stone,  and  coal-tar.  The 
difference  in  the  pavement  was  in  the  wearing  surface,  which  varied 
according  to  the  patents,  but  coal-tar  was  the  cementing  material. 
Some  of  these  failed  very  quickly.  Of  187,271  square  yards  of  the 
Evans  pavement  laid  in  1872-3  at  a  cost  of  $3.20  per  yard,  over- 
150,000  yards  were  resurfaced  within  two  years.  Others  stood 
much  better,  some  not  being  resurfaced  for  six  or  seven  years,  and 
quite  a  number  lasted  even  ten  and  fifteen  years. 

In  the  report  of  the  Engineering  Department  of  the  District  of 
Columbia,  in  1887,  Captain  Griffin  says: 

"  Tne  mean  average  expense  for  maintenance  of  745,305  square 
yards  is  5.5  cents  per  square  yard  for  fifteen  years.  That  a  durable 
coal-tar  pavement  can  be  laid  is  proven  by  the  fact  that  the  vul- 


•    _  ' 

ASPHALT  PAVEMENTS.  213 

canite  pavements  have  only  averaged  2.9  cents  per  square  yard  per 
annum." 

So  expensive  were  these  coal-tar  pavements  to  maintain  that 
Lieutenant  Hoxie,  in  1887,  estimated  that  their  cost  would  be  20 
cents  per  yard  per  annum,  so  that  when  the  first  Board  of  Commis- 
sioners appointed  under  Act  of  June  11,  1878,  came  into  office,  they 
expressed  themselves  as  follows  on  this  subject: 

"  In  determining  the  class  of  pavements  to  be  hereafter  laid> 
the  commissioners  maintain  that  each  class  of  pavement  must 
prove  its  quality  under  test  of  actual  traffic  before  being  exten- 
sively laid  upon  the  streets  of  this  city. 

"  While  some  of  the  later  and  better  class  of  coal-tar  pavements 
show  good  service  and  give  a  fair  promise  of  reasonable  dura- 
bility, yet  the  general  condition  of  this  class  of  pavements  in  the 
city  is  such  as  to  lead  to  their  condemnation  as  faulty  in  principle 
and  deficient  in  vitality. 

"  The  use  of  bituminous  bases  has  also  given  rise  to  many  per- 
plexing problems  in  the  grades  of  streets  upon  which  they  have 
been  laid,  and  as,  when  properly  laid,  their  cost  is  as  great  as,  if 
not  greater  than,  hydraulic  concrete,  they  have  been  definitely 
abandoned." 

In  1886-87  Congress  passed  a  law  which  provided  that  no  con- 
tract  should  be  made  for  making  or  repairing  concrete  or  asphalt 
pavements  at  a  higher  price  than  $2  per  square  yard,  of  a  quality 
equal  to  the  best  laid  in  the  District  prior  to  July  1,  1886,  and  with 
the  same  depth  of  base.  The  lowest  bid  for  asphalt  pavements  re- 
ceived immediately  after  the  passage  of  this  act  was  $2.25,  which 
could  not  be  accepted,  and  the  city  was  obliged  to  return  to  coal- 
tar  pavements  and  those  of  asphalt  block. 

The  specifications  for  these  coal-tar  pavements  provided  that 
the  base  and  binder  should  be  4£  inches  thick  and  laid  as  follows: 

"  The  base  will  be  composed  of  clean  broken  stone  that  will 
pass  through  a  3-inch  screen,  well  rammed  and  rolled  with  a  steam- 
roller, to  a  depth  of  4  inches,  and  thoroughly  coated  with  hot  pav- 
ing-cement composed  of  the  best  No.  4  coal-tar  distillate,  in  the 
proportion  of  about  1  gallon  to  the  square  yard  of  pavement.  The 
second  binder  course  will  be  composed  of  clean  broken  stone  thor- 
oughly, screened,  not  exceeding  1J  inches  in  dimension,  and  No.  4 


214:        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

coal-tar  distillate.  The  stone  will  be  heated  by  passing  through 
revolving  heaters  and  thoroughly  mixed  by  machinery  with  the 
distillate  in  the  proportion  of  one  gallon  of  distillate  to  one  cubic 
foot  of  stone.  The  binder  will  be  hauled  to  the  work,  spread  upon 
the  base  course  at  least  two  inches  thick,  and  immediately  rammed 
and  rolled  with  hand  and  heavy  steam  rollers  while  in  a  hot  and 
plastic  condition.  The  wearing  surface  will  be  1J  inches  thick 
when  compacted,  made  of  paving-cement  composed  of  25  per  cent 
asphalt  and  75  per  cent  coal-tar  distillate,  mixed  with  other  mate- 
rials as  follows: 

"  Clean,  sharp  sand  will  be  mixed  with  pulverized  stone,  of  such 
dimensions  as  to  pass  through  a  J-inch  screen,  in  the  proportion  of 
2  to  1. 

"To  21  cubic  feet  of  the  above-named  mixture  will  be  added 
1  peck  of  dry  hydraulic  cement,  1  quart  of  flour  of  sulphur,  and  2 
quarts  of  air-slacked  lime.  To  this  mixture  will  be  added  320  Ibs. 
of  paving-cement  to  compose  the  wearing  surface." 

This  material  was  laid  on  the  street  in  practically  the  same  man- 
lier -as  asphalt  pavement  is  at  the  present  time. 

The  coal-tar  pavements  laid  in  1887  cost  4.65  cents  per  yard 
per  year  for  maintenance  for  ten  years,  and  those  laid  in  1888  cost 
5.96  cents  per  yard  per  year  for  a  period  of  nine  years.  At  the 
end  of  ten  years  it  was  found  necessary  to  relay  some  of  them  and 
substitute  standard  asphalt,  and  future  repairs  will  be  made  in  the 
same  manner. 

From  a  table  published  in  the  report  of  the  Engineering  De- 
partment of  the  District  of  Columbia,  in  the  fiscal  years  1886-87, 
it  is  'shown  that  the  annual  expenditure  for  the  maintenance  of 
coal-tar  pavements  for  fifteen  years  ending  July  1,  1886,  had  been 
7.2  cents  per  square  yard. 

These  pavements  being  laid  on  a  bituminous  base  become  prac- 
tically a  part  of  the  base,  and  in  repaving  them  it  is  necessary  to 
take  up  the  entire  pavement;  while  if  they  had  been  laid  on  a 
!iydraulic-cement  concrete  base,  it  would  only  have  been  necessary 
to  have  renewed  the  wearing  surface. 

The  fact,  that  these  coal-tar  pavements  did  not  give  complete 
satisfaction,  and  were  expensive  to  maintain,  led  people  interested 
in  the  subject  to  make  experiments  with  other  material. 


ASPHALT  PAVEMENTS:  215 

Mr.  E.  J.  de  Smedt,  who  had  taken  out  several  patents  and  had 
made  many  experiments,  laid  a  bituminous  pavement  in  Newark, 
N.  J.,  in  front  of  the  City  Hall  in  1870,  with  Trinidad  asphalt  as 
the  cementing  material.  This  was  without  doubt  the  first  asphalt 
pavement  laid  in  the  United  States.  It  was  followed  by  another 
similar  one  in  New  York  City  near  the  Battery  in  1871,  and  soon 
-after  by  another  in  Philadelphia,  and  in  a  few  years  still  more  in 
New  York  City.  These  pavements  gave  such  satisfactory  results 
that  they  attracted  the  attention  of  the  authorities  in  Washington, 
and  a  special  commission  was  appointed  by  Congress  to  investigate 
-and  report  as  to  the  advisability  of  adopting  them  in  Washington. 
As  a  result  of  the  commissioners'  report  Pennsylvania  Avenue 
from  First  Street  to  Sixth  Street  was  paved  with  rock  asphalt  by 
the  Neuchatel  Asphalt  Co.  in  1876-77,  and  from  Sixth  Street  to 
Fifteenth  Street  at  the  same  time  with  Trinidad  asphalt.  These 
pavements  gave  good  satisfaction,  except  that  the  rock  asphalt  was 
so  slippery  that  when  the  street  was  resurfaced  in  1890  Trinidad 
asphalt  was  laid  over  the  entire  area.  The  success  of  asphalt  in 
Washington  may  be  considered  as  settling  to  a  great  extent  the  ex- 
perimental nature  of  the  pavement,  and  from  that  time  on  its  suc- 
cess has  been  assured  and  its  use  has  continually  increased. 

In  many  respects  asphalt  makes  a  perfect  pavement.  It  will 
sustain  travel  without  being  damaged,  and  in  fact  is  benefited  by 
quite  severe  traffic.  It  is  smooth,  pleasant  to  drive  over,  almost 
noiseless  for  carriages,  and  can  be  kept  absolutely  clean.  It  is  im- 
pervious to  water  or  moisture  and,  consequently,  as  a  sanitary  pave- 
ment is  without  a  rival.  It  is  considered  by  some  to  be  expensive, 
and  it  is,  as  compared  with  some  of  the  coarser  rock  pavements,  but 
very  few  who  have  once  used  it  are  willing  to  give  it  up,  or  doubt 
that  they  have  received  the  value  of  their  money. 

Many  asphalt  pavements  have  failed,  and  have  required  con- 
siderable resurfacing  sooner  than  they  should;  but  when  it  is  re- 
membered how  new  the  industry  is,  how  rapidly  it  has  been 
developed,  that  there  was  no  precedent  for  the  mixtures,  and  that 
the  principal  mode  of  treatment,  as  well  as  the  percentages  of 
materials  to  be  used,  had  to  be  determined  by  actual  practice  and 
experiment,  the  wonder  is  that  not  so  many  but  that  so  few  pave- 
ments have  failed. 


216        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

One  of  the  objections  made  to  asphalt  is  on  account  of  its- 
slipperiness  and  the  liability  of  horses  falling  when  they  come  off 
from  a  rough  stone  surface  to  the  smooth  asphalt.  There  is  some 
reason  in  this,  but  as  asphalt  pavements  increase  in  quantity,, 
horses  will  become  more  accustomed  to  them  and  learn  to  adapt 
themselves  to  the  smooth  surface.  Asphalt  itself,  contrary  to  the 
general  belief,  is  not  slippery.  It  is  smooth,  and  any  soft  substance 
upon  a  smooth  surface  makes  it  slippery.  Asphalt  pavements 
should  be  kept  clean  and  then  there  will  be  less  trouble  on  account 
of  horses  slipping.  Asphalt  is  much  less  slippery  when  dry  than 
when  slightly  damp  or  moist.  It  is  well  known  to  truckmen  that 
horses  travel  on  a  smooth  pavement  much  more  easily  during  a 
heavy  rain  than  in  a  drizzle.  A  certain  amount  of  street  detritus, 
must  collect  on  any  smooth  pavement,  and  when  rain  falls  in  a 
quantity  sufficient  to  wet  it  only  rather  than  wash  it  clean,  it  must 
be  slippery  to  a  certain  extent. 

The  question  as  to  what  is  the  steepest  grade  on  which  it  is 
safe  to  lay  asphalt  has  received  a  great  deal  of  study.  When  the 
material  was  first  introduced  grades  of  4  per  cent  were  considered 
prohibitory,  and  very  little  was  laid  on  those  exceeding  3  per  cent,, 
but  practice  soon  showed  that  this  was  too  conservative  a  view,  and 
as  a  result  pavements  have  been  laid  successfully  and  quite  fre- 
quently on  grades  as  high  as  7  and  8  per  cent,  and  in  Scranton,  Pa.,, 
there  is  a  portion  of  one  street  that  has  a  grade  of  12  J  per  cent.  It 
was  said  to  have  been  placed  on  this  particular  block  for  the  sake  of 
preventing  traffic,  but,  strange  to  say,  it  has  not  done  so,  and  the 
City  Engineer  says  that  after  several  years'  use  no  great  trouble  has- 
been  experienced  with  it. 

Fig.  13  represents  a  profile  of  a  portion  of  Bates  Street,  Pitts- 
burgh, Pa.  This  shows  that  the  elevation  of  the  grade  increased 
from  188.21  at  the  property  line  to  209.63  at  a  point  200  feet  dis- 
tant, making  an  average  rise  of  10.7  per  cent.  Instead,  however,  of 
making  a  uniform  grade,  these  points  were  connected  by  a  vertical 
curve,  making  in  one  section  a  grade  of  17.1  per  cent,  and  in  the 
first  80  feet  the  minimum  rate  is  12.4  per  cent.  This  street  is 
paved  with  sheet  asphalt,  and  without  doubt  has  the  steepest  grade 
of  any  street  in  the  world  paved  with  that  material. 

As  a  rule,  however,  asphalt  should  not  be  laid  on  a  street  that 


ASPHALT  PAVEMENTS. 


217 


will  be  subjected  to  any  material  amount  of  traffic  on  grades  ex- 
ceeding 6  per  cent,  for  there  must  be  certain  times  of  the  year  when 
they  can  be  used  but  little  and  with  considerable  difficulty.  On  resi- 
dence streets,  however,  where  traffic  is  light,  the  people  are  willing 
in  many  cases  to  put  up  with  the  inconvenience  of  the  slippery 
streets  on  a  comparatively  few  days  of  the  year  for  the  sake  of  hav- 


» 


209.63 


2096 


208.70 


208.13 


207.49 


206.74 


206.02 


205.19 


204.28 


203.31 


202.28 


>OQ.OQ 


198.76    / 
197.45   / 


136.08 


19464 


I93.I4 


191.56  / 


I89.92/ 


T^Y          PROPERTY  UNB 


187.79 


BOUQUET  ST. 


CURB  LINE 


FIG.  13. 

ing  smooth,  clean,  noiseless  pavements  for  the  remainder  of  the 
time. 

In  New  York  City,  where  a  street  has  been  paved  on  a  6  per 
cent  grade  with  asphalt  on  the  sides  and  granite  in  the  centre,  as  a 
rule  the  traffic  seeks  the  smooth  asphalt  with  its  ease  of  traction, 
rather  than  take  the  granite. 

Asphalt  pavements  are  now  in  use  upon  grades  in  different  cities 
as  shown  on  page  218. 


218        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


Per  cent. 

New  York  City 6 

Omaha,  Nebraska 7  to  8 

Brooklyn,   N.  Y 4y2 

Syracuse,  N.  Y 7 

Scranton,   Pa ' 12y2 

The  crown  of  pavements  has  been  thoroughly  discussed  in  the 
chapter  on  Stone  Pavements,  and  the  remarks  made  there  will  apply 
with  equal  force  to  asphalt. 

Table  No.  60  shows  the  method  adopted  by  the  Department  of 
Highways  in  the  Borough  of  Brooklyn,  New  York  City,  for  laying 

TABLE  No.  60. 

CKOSS-SECTIONS  TO  BE  USED  IN  LAYING  ASPHALT  PAVEMENTS  ;  SHOWING 
MEASUREMENTS  FROM  A  LINE  DRAWN  FROM  CURB  TO  CURB  TO  THE 
FINISHED  PAVEMENT. 

Measurements  to  Finished  Surface. 


Curb. 

%             K 
from,      from 

Centre. 

M 

from. 

% 
from. 

Curb 

4"  GUTTERS. 

Centre  2"  above  line      (6"  crown) 

"       1"       "        "          (5"       "      ) 
even  with  "         (4"       "     ) 

4" 

V 

9tff'f 

154"  ab. 
V^"  above 
J£ 

2"  above 
1"   above 
0 

1M"  ab. 
j-^"  above 

f 

4" 

4" 

4" 

4"  X  5"  GUTTERS. 

Centre  1J^  above  line  (6^'  crown) 
£f"  below    "      (4"       "     ) 

4//     1     WH 

1"  above 
0 
'n 

I«"  ab. 
H"  above 

34"  above 
H7 

^' 

2^" 

5" 
5" 
6" 

4"  x  6"  GUTTERS. 

Centre  1"  above  line       (6"  crown) 
"      even  with"         (5"             ) 
"      1"  below    "         (4"             ) 

4" 
4" 
4" 

\" 
$?' 

W  above 

r 

\"  above 
0 

1" 

0 

1" 

w 

2^4" 
3" 
3V^" 

6" 
6" 
6" 

4"  x  7"  GUTTERS. 

Centre  \y  above  line     (6"  crown) 
||      Wf'f  below    ||       (5JJ       ||     ) 

4" 
4" 
4" 

s 

J4"  above 

%" 

W  above 
l^/:' 

%"  above!  3^" 
l^y/       »f" 
2^1"      IS" 

7" 

4"  X  8"  GUTTERS. 

Centre  even  with  line     (6"  crown) 
"      1"  below     "       (5"      "     ) 

»          y,         «                ,«           fa          «        ) 

4" 
4" 
4" 

w 
w 

0 

lx/ 

1%" 

0 

1" 
2" 

1^4" 
a^" 

3^ 

4" 

^" 

8" 
8" 

H" 

4"  X  9"  GUTTERS. 

Centre  U"  below  line     (6"  crown) 
"     1V$"       "        "        (5"       "      ) 
"     2!4"       "        "        (4"       "      ) 

4" 
4" 
4" 

jr 

2H" 

f 

«" 
1&" 

2^" 

2" 
3" 
S«" 

e"" 

9" 
9" 
9" 

5"  GUTTERS. 

Centre  1"  above  line      (6"  crown) 
"       even  with  "         (5"       "      ) 
»       1"  below    "         (4"       "     ) 

5"    1  1^" 
5"      2^" 
5"    |2%" 

J4"  above 

^ 

1"   above 
0 
1" 

Hx'  above 

]^' 

W 
2^7/ 
294" 

5" 
5" 
5" 

6"  GUTTERS. 

Centre  even  with  line     (6"  crown) 
"      1"  below      "       (5"       "     ) 

"       2"      »            »       (4"       "      ) 

6" 
6" 
6" 

W 
*W 
3%" 

i 

0 

1" 
2" 

i 

2%" 
3>/2" 
3%" 

6X/ 
6" 
6" 

ASPHALT  PAVEMENTS.  219 

out  the  cross-section  of  asphalt  pavements  with  different  depths  of 
gutter,  the  surfaces  being  obtained  in  the  same  manner  as  with 
stone  pavement,  by  measuring  down  at  stated  intervals  from  a  line 
stretched  from  curb  to  curb. 


Character  of  Asphalt. 

To  make  a  first-class  pavement,  asphalt  should  be  of  a  good 
character,  properly  mixed  with  the  right  materials,  and  well  laid 
upon  a  good  foundation.  Whether  untried  asphalt  will  or  will  not 
make  a  good  pavement  can  only  be  settled  by  actual  use.  A  chemist 
can  analyze  it,  tell  what  are  its  component  parts,  give  its  physical 
properties,  as  well  as  his  idea  as  to  what  it  ought  to  do,  but  cannot 
tell  positively  how  it  will  act  in  a  pavement.  The  asphalt  on  Eighth 
Avenue,  New  York  City,  laid  in  1890,  probably  has  received  more 
notice  than  that  laid  on  any  other  street  in  this  country.  Stephen- 
son  Towle,  at  that  time  Consulting  Engineer  of  New  York,  in 
speaking  of  this  pavement  in  his  report  to  the  Commissioner  of 
Public  Works  in  January,  1895,  said: 

"  This  asphalt  was  submitted  to  and  approved  by  experts  and 
chemists  before  the  contract  was  entered  into.  Soon  after  the  pave- 
ment was  laid,  and  before  its  completion  [it  has  never  been  ac- 
cepted], it  showed  unmistakable  evidences  of  disintegration.  This 
failure  was  exceptional,  and  the  experts  and  chemists  who  had  ap- 
proved of  the  asphalt  could  not  account  for  it.  My  own  belief  was 
that  the  asphalt  was  inferior  or  lacking  in  some  essential  property 
unknown  to  chemists." 

While  all  asphalt  contains  bitumen,  all  bitumen  will  not  make 
a  good  pavement,  no  matter  with  what  it  is  fluxed.  Certain  varie- 
ties of  asphalt  will  be  brittle  and  not  possess  the  cementitious 
properties  necessary  to  hold  the  sand  together.  An  asphalt  pave- 
ment is  really  an  asphaltic  concrete  in  which  particles  of  sand  are 
held  together  by  the  cementing  properties  of  the  asphalt,  and  if  for 
any  reason  the  asphalt  loses  the  cementing  properties,  the  pavement 
must  disintegrate  and  fail.  Some  asphalts,  however,  while  not 
suitable  for  pavements  in  themselves,  can,  by  being  mixed  with 
proper  quantities  of  other  bitumens  by  people  who  understand  the 
nature  of  the  material,  be  made  into  a  valuable  cementing'  sub- 


220        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

stance.  A  poor  asphalt  treated  by  an  expert  is  liable  to  make  a  bet- 
ter pavement  than  good  material  handled  by  poor  and  inexperienced 
workmen.  A  new  asphalt  should  be  laid  two  or  three  years  at  least 
before  it  is  safe  to  pass  an  opinion  upon  it  as  to  its  durability.  If 
laid,  as  it  generally  is,  in  the  summer,  the  winter  season  subjects 
the  material  to  a  severe  test.  The  cold  weather  causes  it  to  con- 
tract, and  if  laid  too  hard,  it  is  apt  to  crack  and,  if  the  cold  con- 
tinues, crumble  to  a  certain  extent.  In  a  previous  chapter  reference 
has  been  made  as  to  the  proper  method  for  the  chemist  to  examine 
new  asphalts. 

Asphaltic  Cement. 

Very  few  asphalts  now  on  the  market,  and  probably  but  one, 
are  fit  to  be  used  in  pavements  after  they  are  refined.  Used  as  they 
come  from  the  refinery,  the  resulting  pavements  would  soon  disin- 
tegrate. Consequently  they  must  be  mixed  with  certain  fluxing 
materials  which  will  dissolve  the  asphaltine  and  cause  the  whole 
mass  to  form  a  soft,  tough  cementing  material.  This  is  called 
asphaltic  cement.  The  early  asphalt  pavements  and  the  greater 
part  of  those  in  use  at  the  present  time  were  laid  with  asphaltic 
cement  formed  of  refined  asphalt  and  petroleum  residuum.  In  later 
times,  since  the  discovery  of  asphalt  in  California,  and  bitumen  in  a 
softer  state,  such  as  maltha,  and  in  even  a  still  lighter  form,  quite 
a  considerable  amount  of  the  refined  product  has  been  fluxed  with 
maltha  and  asphaltic  oils.  Considerable  controversy  has  arisen  as 
to  the  relative  values  of  these  different  fluxes.  Mr.  A.  W.  Dow, 
Inspector  of  Asphalts  and  Cements  in  the  District  of  Columbia,  and 
Mr.  Clifford  Eichardson,  chemist  for  the  Barber  Asphalt  Co.,  have 
probably  investigated  this  particular  subject  more  thoroughly  than 
any  one  else,  and  have  arrived  at  almost  diametrically  opposite  re- 
sults. In  a  paper  prepared  by  Mr.  Eichardson  and  published  in 
Municipal  Engineering  in  1897,  after  detailing  some  experiments 
he  says: 

"  The  most  successful  proof  of  the  solubility  of  the  bitumen  and 
asphalt  in  residuum  oil  was  reached  by  preparing  a  pure  bitumen 
of  both  Trinidad  and  Bermudez  asphalts.  This  was  done  by  dis- 
solving each  in  chloroform  and  removing  everything  insoluble  by 


ASPHALT  PAVEMENTS.  2*21 

subsidation,  filtering,  and  the  use  of  the  centrifugal.  With  this 
pure  bitumen  the  same  percentage  of  the  pure  residuum,  made  as 
nad  been  previously  described,  was  mixed  as  thereafter  used  in 
practice,  in  the  proportion  of  the  ordinary  asphalt  cement.  There 
being  no  impurities  present,  it  was  possible  to  determine  by  ex- 
amination of  the  resulting  mixture  under  the  microscope  with  a 
very  high-power  objective,  1/12  homogeneous  immersion,  whether 
.solution  had  taken  place  or  not.  In  each  case  a  perfectly  homo- 
geneous substance  was  seen  and  entire  solution  had  taken  place. 
Whether  separation  would  take  place  on  a  reduction  of  the  tempera- 
ture, or  with  age,  was  then  determined.  When  the  residuum  con- 
tained much  paraffine  scale  there  was  a  very  slight  evidence  of  the 
presence  of  paraffine  at  a  temperature  below  freezing,  but  ordin- 
arily nothing  separated.  After  three  years'  preservation,  at  ordinary 
temperatures,  the  pure  asphalt  cement  was  as  homogeneous  and 
uniform  as  when  first  made.  The  solution  still  remained  com- 
plete/' 

Summing  up,  among  his  conclusions  he  says: 

"  Residuum  oil  is  perfectly  miscible  with  and  a  satisfactory 
solvent  for  asphalt.  It  does  not  separate  from  asphalt  cements 
when  they  are  properly  made.  It  remains  of  very  soft  consistency, 
and  of  value  as  a  fluxing  agent,  even  after  heating  for  many  hours 
at  high  temperatures." 

In  speaking  of  maltha  and  asphaltic  oils  he  says: 

"  They  have  been  proved  to  be  most  unsuited  and  unsafe  for 
use  as  fluxing  agents,  because  they  are  gradually  changed  in  con- 
sistency in  heating  at  temperatures  at  which  asphalt  cement  is 
usually  held  when  melted.  They  are  finally  turned  into  glassy 
glance  pitch,  having  no  fluxing  value.  They  are  composed  of  un- 
stable and  easily  volatile  hydrocarbons.  They  are  neither  fluxes 
nor  asphalts  for  forming  cement  which  can  be  maintained  of  any 
constant  consistency,  and  it  generally  goes  into  the  work  upon 
which  it  is  employed  either  too  hard  or  too  soft." 

On  the  other  hand,  Mr.  Dow,  in  speaking  of  some  experiments 
which  he  had  made  with  Trinidad  asphalt  and  residuum  oil,  says: 

"  From  the  above  it  is  very  evident  that  there  is  a  marked  dif- 
ference in  the  bitumen  that  filtered  through  and  that  left  -in  the 
iilter.  In  taking  this  result  and  its  proper  microscopic  examina- 


222        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

tion  of  the  filtrate,  we  are  led  to  the  conclusion  that  a  bitumen 
Trinidad  asphalt  is  not  completely  soluble;  that  it  is  more  soluble 
in  hot  residuum  than  in  cold;  and  that  the  extra  amount  that 
enters  into  solution  on  heating  separates  out  on  cooling."  After 
making  a  number  of  experiments  with  mixtures  corresponding  to 
those  used  on  the  street  and  giving  their  results  in  a  table,  he- 
further  says: 

"  On  examining  these  results,  we  find  in  the  case  of  the  two 
cements  made  with  petroleum  residuum  that  several  per  cent  of 
the  asphalt  bitumen  has  been  rendered  insoluble  by  the  addition 
of  the  residuum,,  and  that  this  insoluble  bitumen  is  held  in  sus- 
pension and  will  settle  out  as  so  much  inert  material.  It  is  im- 
possible to  even  approximate  the  amount  of  insoluble  bitumen, 
but  it  must  be  quite  some  more  than  has  settled  in  these  experi- 
ments. It  is  only  reasonable  to  believe  that  proportionately  less 
of  it  would  settle  than  of  the  mineral  ingredients,  and  there  are 
still  quite  some  of  these  held  in  suspension.  Combining  with  all 
these  what  we  learn  in  the  previous  experiment  [that  more  of  the 
asphalt  bitumen  was  soluble  in  hot  residuum  than  in  cold],  the- 
quantity  of  this  residuum  insoluble  in  the  residuum  at  normal 
temperature  must  be  considerable.  In  the  case  of  a  cement  of 
asphaltic  oil  we  find  that  even  though  there  was  quite  as  much 
mineral  matter  subsidized,  yet  the  bitumen  is  a  uniform  composi- 
tion throughout  the  tube,  showing  a  complete  solution.  Judging- 
from  the  physical  properties  of  petroleum  residuum  and  its  chemi- 
cal relation  to  asphaltic  bitumen,  it  is  not  a  desirable  flux,  but  it 
should  not  be  judged  too  strongly  in  the  absence  of  physical  tests 
carried  on  with  the  asphalt  cement  made  with  it." 

When  two  such  diametrically  opposite  opinions  are  given  by 
experts  who  are  honestly  seeking  truth,  it  only  remains  for  the- 
engineer  to  take  what  he  is  satisfied  will  give  good  results,  and 
leave  fine  questions  of  distinction  to  be  decided  by  chemists.  What 
is  positively  known  is  that  good  pavements  have  been  made  with 
both  petroleum  residuum  and  maltha  and  asphalt  oils  as  fluxes.  It 
seems  a  radical  statement  to  say  that  a  flux  that  has  produced  such 
pavements  as  the  asphalt  pavements  of  the  last  fifteen  years  is  not 
the  proper  material  to  be  used.  Whether  it  is  the  best  or  not  is 
another  question.  Until  that  is  definitely  determined,  the  advo- 


ASPHALT  PAVEMENTS.  223 


cates  of  both  will  continue  the  use  of  the  one  that  is  most  con- 
venient to  them. 

When  petroleum  residuum  is  used  as  a  flux  it  is  sometimes 
first  mixed  with  a  so-called  asphalt,  often  termed  "  Pittsburg  flux." 
The  Washington  reports  say  that  a  pavement  was  improved  by  this 
process,  and  that  the  asphaltic  cement  was  made  by  mixing  100  Ibs. 
of  refined  asphalt,  14  Ibs.  residuum,  and  11  Ibs.  Pittsburg  flux. 
Pittsburg  flux  is  manufactured  by  heating  petroleum  residuum  with 
sulphur,  the  sulphur  combining  with  portions  of  the  hydrogen  of 
the  petroleum  and  escaping  as  hydrogen  sulphide  gas,  leaving  the 
product  as  a  residue.  The  usual  amount  of  residuum  used  to  flux 
Trinidad  asphalt  is  about  18  Ibs.  of  oil  to  100  Ibs.  of  refined  asphalt. 
When  maltha  and  asphaltic  oils  are  used,  the  amount  must  be 
determined  both  by  the  character  of  the  flux  and  also  of  the  re- 
fined asphalt. 

Whatever  the  character  of  the  crude  and  refined  asphalt,  it  is 
the  asphaltic  cement  upon  which  the  success  of  the  pavement  de- 
pends. The  asphaltic  cement  should  be  tough  and  elastic;  should 
be  adhesive  so  as  to  hold  the  particles  of  sand  together,  and  co- 
hesive so  as  not  to  disintegrate.  It  should  be  capable  of  resisting 
changes  of  temperature  of  over  30°  below  zero  and  140°  above,  as. 
it  will  in  many  instances  be  subjected  to  these  temperatures  in  pave- 
ments. Observations  taken  in  Washington  when  the  temperature 
of  the  air  was  104°,  about  2  feet  above  the  pavement,  showed  the 
asphalt  itself  to  be  at  a  temperature  of  140°,  while  the  tempera- 
ture of  macadam  at  the  same  time  was  118°.  In  St.  Paul,  Minn.,. 
and  Omaha,  Neb.,  pavements  in  the  winter  will  be  subjected  to 
temperatures  of  30°  below  zero,  although  not  very  often.  It  would 
be  quite  safe  to  predict  that  an  asphaltic  cement  that  would  com- 
ply with  the  conditions  as  given  above  would  make  a  good  pave- 
ment. 

In  order  to  establish  some  standard  for  asphaltic  cement,  in 
1888  Prof.  Bowen,  who  was  then  chemist  for  the  Barber  Asphalt 
Paving  Co.,  devised  an  apparatus  for  determining  the  softness,  or 
viscosity  (as  chemists  prefer  to  call  it),  of  asphaltic  cements.  The 
object  of  this  machine,  and  the  principle  on  which  the  standard 
is  based,  is  to  determine  how  far  a  needle  will  penetrate  the 
asphaltic  cement  at  a  standard  temperature  in  a  given  time.  The 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

needle  is  weighted  with  a  100-gram  weight  and  allowed  to  pene- 
trate the  cement  for  one  second.  The  needle  is  inserted  in  the 
•end  of  a  weighted  lever.  This  lever  is  suspended  by  a  thread  from 
a,  spindle  around  which  it  is  wrapped.  At  one  end  of  the  spindle 
a  pointer  is  fastened  which  indicates  on  a  dial  the  distance,  up 
or  down,  moved  by  the  lever-arm  to  which  the  needle  is  attached. 
On  the  spindle  there  is  a  small  drum,,  around  which  the  thread  is 
wound  supporting  the  weight,  which  acts  as  a  partial  counter- 
balance to  the  weight  of  the  lever.  This  counterweight  keeps  the 
lever-thread  tight,  and  when  the  lever-arm  is  raised  it  returns  the 
pointer  to  the  dial.  The  viscosity  of  the  sample  is  determined  by 
placing  one  end  of  the  needle,  which  is  then  lowered  upon  its  point, 
so  as  to  just  touch  the  surface  of  the  asphalt.  The  position  of  the 
pointer  of  the  dial  is  noted,  the  clamp  released,  and  the  needle 
allowed  to  penetrate  into  the  sample  for  a  fixed  time.  At  the  end 
of  the  time  the  clamp  is  closed  and  the  distance  the  needle  has 
penetrated  can  be  read  from  the  dial,  which  for  convenience  is 
divided  into  360  equal  parts,  and  the  number  of  these  parts  which 
the  needle  has  moved  represents  the  penetration  of  the  cement. 

This  is  an  arbitrary  standard,  but  it  has  been  used  successfully 
in  some  twenty-five  or  thirty  laboratories  or  paving-yards. 

Before  testing  the  samples,  they  should  be  kept  at  a  standard 
temperature  for  a  sufficient  time  to  allow  them  to  attain  the  de- 
sired temperature.  The  temperature  which  has  been  generally 
taken  as  the  standard  is  77°  Fahr.,  and  the  simplest  way  to  main- 
tain the  sample  at  the  proper  temperature  is  by  immersing  it  in 
Crater  which  is  .kept  at  that  temperature. 

Mr.  Dow  has  adopted  a  somewhat  different  method  of  testing 
the  viscosity  by  a  machine  that  is  somewhat  complicated.  His 
standard  is  the  distance  expressed  in  hundredths  of  a  centimeter 
that  a  No.  2  needle  will  sink  or  penetrate  into  the  asphalt  paving- 
•cement  in  5  seconds  when  weighted  with  100  grams,  the  cement  and 
apparatus  being  at  a  temperature  of  25°  C.  This  makes  an  absolute 
and  positive  standard,  but  requires  a  delicate  apparatus  for  the 
measurement.  Under  the  Bowen  standard  the  penetration  of  the 
asphaltic  cement  used  in  Washington  by  the  Barber  Co.  in  1897  was 
85,  and  by  the  Cranford  Paving  Co.  77;  in  1898  by  the  Barber 
Paving  Co.  91,  and  by  the  Cranford  Paving  Co.  83.  In  1889,  when 


ASPHALT  PAVEMENTS.  225 

Mr.  Dow  used  the  standard  just  described,  the  penetration  of  the 
paving-cement  by  the  Eastern  Bermudez  Paving  Co.  was  45,  and  by 
the  Cranford  Co.  36,  showing  that  in  absolute  figures  the  latter 
standard  gives  a  less  result  than  the  former,  but  it  must  be  remem- 
bered that  the  Bowen  standard  was  wholly  arbitrary,  while  that  of 
Mr.  Dow  is  absolute. 

When  it  is  remembered  that  only  about  10  per  cent  of  the  so- 
called  asphalt  pavement  is  made  up  of  bitumen,  it  can  be  readily 
understood  that  it  is  necessary  to  select  the  best  possible  material 
for  the  remainder.  Whatever  this  material  may  be,  it  must  sustain 
the  traffic  to  which  the  pavement  is  subjected.  Stone  in  some 
form  has  been  settled  upon  as  the  best  material,  but  there  has  been 
more  or  less  controversy  always  as  to  the  size  of  the  particles,  and 
also  as  to  how  they  should  be  graded.  A  hard  material  is  abso- 
lutely necessary,  and  the  particles  must  not  be  too  large,  else  under 
the  action  of  the  horses'  shoes  the  stone  will  pick  up  and  leave 
-appreciable  voids  in  the  pavement  which  will  cause  it  to  crumble 
and  wear  away.  As  has  been  said  before,  quite  large  stones  have 
been  used,  but  the  experience  of  the  last  twenty  years  has  demon- 
strated very  satisfactorily  that  a,  hard  silicious  sand  is  the  best 
material  than  can  be  obtained.  In  a  paper  read  before  the  Ameri- 
can Society  of  Municipal  Improvements,  in  1898,  Mr.  Dow  went 
very  carefully  into  the  character  and  size  of  sands  that  should  be 
used.  He  first  demonstrated  that  asphalt  cements  are  liquid,  and 
basing  his  argument  upon  the  fact  that  fine  beach-sand,  when  wet 
with  water,  is  almost  solid,  while  the  coarser  sand  is  soft.  He  goes 
on  to  say: 

"  Looking  at  asphalt  cement  as  liquid,  we  should  expect  to  find 
analogous  results  when  paving  mixtures  are  made  with  these  two 
sands,  using  with  each  the  same  asphalt  cement;  that  the  mixture 
made  with  the  finer  sand  would  be  harder  than  that  made  with 
the  coarser  (this  is  what  we  find  in  practice),  while  by  using  a  much 
softer  asphalt  cement  with  the  finer  sand  and  with  the  coarser 
equally  hard  mixtures  are  produced.  The  cause  of  this  is  ex- 
plained by  the  fact  that  the  voids  of  the  finer  sand  are  much 
smaller  in  size,  which  means  that  the  sand-grains  are  closer  to- 
gether. It  is  a  well-known  fact  that  the  smaller  the  space  betwepri 
two  solid  bodies  that  are  held  together  by  the  attraction  of  a  liquid 


226        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

between  them,  the  greater  the  adhesion.  There  are  two  grades 
of  sand  that  have  small  voids;  one  is  composed  of  very  fine  grains,, 
and  the  other  is  a  sand  with  the  grains  so  graded  from  coarse  to 
fine  that  all  of  the  large  voids  are  filled  with  smaller  grains  and 
their  voids  in  turn  filled  with  still  finer.  The  latter  is  the  most 
desirable  sand,  for  several  reasons.  Among  them  are:  It  is  very 
easily  handled  in  the  manufacture  of  the  pavement,  and  it  re- 
quires less  asphalt  cement,  not  alone  because  the  per  cent  of  fine 
is  less,  but  the  total  surface  area  of  the  sand-grains  is  smaller." 

It  will  be  noticed  in  this  conclusion  of  Mr.  Dow  that  he  argues 
in  practically  the  same  way  as  one  might  in  relation  to  cement 
concrete,  and  really  the  principle  is  the  same.  The  wearing  sur- 
face of  the  asphalt  pavement  is  a  concrete  in  which  the  bituminous 
substance  is  the  cementing  matter  rather  than  the  hydraulic 
cement.  Mr.  Dow  further  goes  on  to  illustrate  the  differences  in 
result  when  different  sizes  of  sand  are  used  by  referring  to  the 
pavement  in  Washington  laid  in  1894,  which  he  said  marked  as 
much,  if  not  more  than,  those  laid  in  1897,  and  some  of  the  former 
cracked  in  cold  weather.  The  asphalt  cement,  however,  with  which 
the  1897  pavement  is  laid  was  found  to  be  20°  harder  than  that 
used  in  1894.  Consequently  he  inferred  that  the  difference  must 
be  due  to  the  sand.  Upon  a  trial,  the  sand  was  found  to  be  graded 
as  follows: 

TABLE  No.  61. 

1SP4  1897. 

Retained  on  20  mesh  per  linear  inch. .  4.5  2.5 

40       "        "  "           "    ..  40.0  21.0 

60       "        "  "           "    ..  32.0  35.0 

80       "        "  "           "    ..  9.5  8.5 

100       "        "  "           "    ..  6.0  10.0 

Passing     100       "       "  "          "    . .  8.0  24.0 

He  also  refers  to  the  well-known  fact  that  the  European  rock 
pavements,  the  durability  of  which,  without  doubt,  is  greater  than 
that  of  the  American  pavements,  is  made  up  of  a  limestone  powder, 
cemented  together  by  asphalt  so  soft  that  its  flow  is  perceptible  at 
a  temperature  of  75°,  which  is  three  times  softer  than  any  asphalt 
cement  used  at  present  in  American  pavements.  It  is  also  well 
known  to  all  persons  engaged  in  asphalt  paving  that  the  European 
rock  asphalts  are  much  harder  on  the  street  at  the  same  air-tern- 


ASPHALT  PAVEMENTS. 


227 


perature  than  the  pavements  in  this  country.  He  also  says  that 
angular  and  not  rounded  sand  should  be  used,  as  the  angular  sand 
packs  much  more  solidly  and  gives  a  correspondingly  harder  pave- 
ment. All  of  the  sand  used,  of  whatever  sizes,  should  be  hard  and 
solid. 

Table  No.  62  shows  sands  used  in  different  cities. 

TABLE  No.  62. 

SHOWING    SIZE   OF    DIFFERENT    SANDS    USED   BY   VARIOUS   ASPHALT   PAVING 

CONTRACTORS. 


Contractor. 

City. 

! 

Percentages  Retained  by  Sieves. 

10-mesh. 

I 

| 

60-mesh. 

! 

.G 

1 

*15 
*13 
*24 
*19 

*26 
*18.5 

*15 
*«.53 

*23.19 

*21.95 
3.51 

18.70 

10.26 
32.65 
*18.70 

Passing 
200-mesh 

Barber  Paving  Co..  .  . 
€ranford  Paviug  Co. 
Barber  Paving  Co.  ... 
•Cranford  Paving  Co. 
Eastern      Bermudez 
Paving  Co 

Washington 

Brooklyn 
M 

Toronto,  Can. 
Brooklyn 

1897 
189? 

1SJJS 

1898 

1899 
1899 

1898 
1896 

1896 

1896 
1898 

1898 

1898 
1>99 
1888 

0 
7.39 

0.5 

2.18 

2.87 

0.9 

0.36 
0 
13.25 

2.5 
3.5 
2.5 
3.5 

2.5 
3 

12 

16.98 

8.95 

10.52 
13.22 

2.61 

6.74 
.24 

18.21 

24.5 
27 

21 

29 

20 
26.5 

25 
27.26 

26.68 

27.1? 
29.07 

11.26 

20.93 
2  69 
24.34 

31 
32.5 
35 
33 

31.9 
38.3 

20 

18.87 

29.16 

26.58 
27.23 

16.30 

27.04 
11.80 
16.15 

16 
15 

8.5 
7 

8.3 
7.0 

10 
5.80 

9.95 

9.54 
6.47 

7.38 

7.99 
10.85 
3.68 

11 
10 
10 

8 

10.8 
6.5 

18 
1.17 

2.02 

2.06 
7.25 

24.24 

10.04 
24.72 
5.60 

10.  3S 
19.42 

16.64 
17.05 

Cranford  Paving  Co. 
Recommended       by 
Mr.  Dow  
€ranford&  Co  
Eastern      Bermudez 
Asphalt  Paving  Co. 
Brooklyn      Alcatraz 
Asphalt  Co  

CJrantord  &  Co      .... 

Eastern      Bermudez 
Asphalt  Paving  Co. 
Brooklyn      Alcatraz 
Asphalt  Co  

*  Passing  100-mesh. 

Wearing  Surface. 

The  wearing  surface  of  the  asphalt  pavement  should  be  abso- 
lutely impervious  to  water.  Unless  it  is  so,  in  wet  weather  the 
moisture  will  soak  into  the  material  and  the  oxygen  in  the  water 
will  oxidize  the  asphalt,  changing  the  petrolene  into  an  asphaltene 
and  thus  causing  premature  disintegration.  In  order  to  make  this 
more  certain,  it  has  always  been  customary  to  mix  with  the  sand 
a  certain  amount  of  mineral  matter.  As  carbonate  of  lime  was 
first  used,  it  was  thought  that  there  was  some  chemical  action  be- 
tween the  bitumen  and  carbonate,  and  for  that  reason  it  should  be 


228        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

used  rather  than  any  other  fine  material,  but  this  idea  is  pretty 
well  exploded  at  the  present  time,  and  paving  experts  generally 
believe  that  a  pulverized  silica  is  as  good  as,  if  not  better  than,  car- 
bonate of  lime.  Carbonate  of  lime  has  a  tendency,  especially  if 
used  in  excess,  to  make  the  pavement  hard  and  slippery,  and  in 
fact  to  some  extent  of  the  nature  of  a  rock  asphalt,  while  a  silicious, 
powder  will  make  the  resulting  pavement  less  slippery,  and  in  the 
last  two  or  three  years  a  great  many  pavements  have  been  laid  with 
this  rather  than  with  pulverized  limestone,  with  invariably  good 
results.  It  would  have  been  used  even  more  if  it  could  have  been 
obtained  as  readily  and  as  cheaply.  The  wearing  surface,  then> 
of  the  asphalt  pavement  is  made  up  of  asphaltic  cement,  sand,  and 
pulverized  mineral  matter.  If  these  materials  have  all  been  selected 
and  manufactured  with  care,  the  next  thing  to  be  considered  is  the 
proportion  in  which  they  should  be  mixed. 

The  powdered  mineral  matter  should  be  of  such  degree  of  fine- 
ness that  16  per  cent  of  it  by  weight  will  be  an  impalpable  powder,, 
and  the  whole  of  it  should  pass  a  No.  30  screen.  The  exact  quantity 
to  be  used  must  be  determined  by  the  gradation  of  the  sand,  as  the 
object  of  the  mineral  matter  is  to  fill  the  voids  in  the  sand  so  as. 
to  make  the  total  voids  as  small  as  possible.  The  amount  gener- 
ally used  is  from  4  to  8  per  cent.  The  amount*  of  paving-cement  re- 
quired depends,  first,  upon  the  character  of  the  cement,  and,  second, 
upon  the  voids  in  the  combined  sand  and  mineral  powder. 

Refined  Trinidad  asphalt  contains  about  55  per  cent  bitumen,, 
refined  Alcatraz  about  80  per  cent,  and  refined  Bermudez  about 
90  per  cent.  So  that  whatever  the  nature  of  the  fluxes  by  which 
asphaltic  cement  is  made  from  either  of  these  asphalts,  the  re- 
sulting cement  must  vary  greatly  in  the  amount  of  bitumen  con- 
tained if  the  same  amount  of  asphalt  is  used.  It  is  admitted 
at  the  present  time  that  the  wearing  surface  should  contain, 
speaking  generally,  about  10  per  cent  of  bitumen,  and  at  all 
events  not  less  than  8-|  or  9  per  cent,  although  in  some  ex- 
ceptional cases  good  pavements  have  been  in  existence  for  some 
years  where  the  analysis  showed  not  more  than  7  per  cent  bitumen. 
Consequently,  in  order  to  obtain  9  per  cent  of  bitumen  in  any  mix- 
ture, more  Trinidad  cement  will  be  required  than  Alcatraz,  and 
more  Alcatraz  than  Bermudez.  One  asphalt  company  in  giving  direc- 


ASPHALT  PAVEMENTS.  229 

tions  for  the  determining  of  the  actual  amount  of  asphaltic  cement 
says:  "  Take  the  known  weight  of  the  sand  and  powdered  carbonate 
of  lime,  previously  deprived  of  water  and  thoroughly  mixed  in  the 
proportions  determined  upon.  Place  same  in  a  large  tin  or  iron 
bucket;  add  water  until  no  more  can  be  absorbed  and  until  the  voids 
are  all  filled  with  water,  and  no  more.  The  resulting  increase  in 
weight  will  of  course  give  the  weight  of  water  necessary  to  fill  the 
voids  of  so  many  pounds  of  sand  and  powdered  limestone.  Multiply 
the  weight  of  the  water  thus  obtained  by  the  specific  gravity  of 
the  asphalt,  and  the  result  will  be  the  least  amount  by  weight  of 
asphalt  cement  required  to  fill  the  voids  of  the  known  weight  of 
sand  and  mineral  matter."  In  illustrating  this  they  say:  "  Let 
us  suppose,  for  example,  that  50  Ibs.  of  sand  and  6  Ibs.  of  powdered 
limestone  were  found  to  absorb  5l  /2  ^s-  °f  water.  In  that  case, 
since  51/2  times  11/10  (the  specific  gravity  of  that  particular 
asphalt)  equals  65/100,  the  resulting  mixture  should  be: 

50  Ibs.  sand 

6  Ibs.  carbonate  of  lime 

65/100  Ibs.  asphaltic  cement 

Total,     625/ioolbs- 

Or,  reducing  these  figures  to  a  percentage  basis,  we  have  practi- 
cally: 

80  parts  by  weight  of  sand 

10  parts  by  weight  of  carbonate  of  lime 

10  parts  by  weight  of  asphalt  cement 

100" 

Thickness  of  the  Wearing  Surface. 

After  determining  upon  the  composition  of  the  wearing  surface, 
it  will  next  be  proper  to  decide  upon  its  thickness.  A  certain 
amount  of  the  paving  material,  of  whatever  kind,  must  always  be 
wasted  when  a  pavement  is  relaid.  It  is  never  possible  to  get  the 
entire  amount  of  wear  out  of  the  whole  surface,  so  it  is  not  economy 
to  lay  a  greater  thickness  than  can  be  used  to  advantage.  If  the 
thickness  of  the  wearing  surface  be  too  great,  it  will  not  be  possible 


230        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

to  give  it  proper  compression  under  the  roller,  and  consequently  the 
entire  amount  of  material  will  not  be  used,  and  in  fact  the  pave- 
ment will  be  more  likely  to  fail  than  if  the  portion  actually  com- 
pressed was  laid  upon  a  solid  base  rather  than  the  softer  asphalt 
which  was  not  compressed.  In  actual  practice  it  has  been  found 
that  a  compressed  asphalt  of  2  inches  gives  the  best  satisfaction. 
This  requires  the  material  to  be  spread  loosely,  as  it  is  brought 
upon  the  street,  to  a  depth  of  about  2J  inches.  In  light-traffic 
streets  the  surface  is  sometimes  made  1-J  inches  thick,  but,  on  the 
principle  laid  down  above  as  to  the  economical  wear  of  the  entire 
amount  laid,  it  would  seem  that,  even  if  the  travel  be  light,  it  would 
be  true  economy  to  lay  a  pavement  of  such  thickness  as  could  be 
thoroughly  compressed.  Methods  and  proportions  for  mixing  will 
be  discussed  later  on. 

Binder. 

The  first  asphalt  pavements  were  laid  2J  inches  thick,  with  a  so- 
called  J-inch  cushion-coat  laid  first  and  rolled  upon  the  concrete, 
and  a  top  coat  2  inches  thick  laid  upon  that.  If  the  concrete  con- 
tained any  appreciable  amount  of  moisture  when  the  hot  cushion- 
coat  was  laid  upon  it,  the  moisture  was  evaporated  into  steam  and 
bubbles  formed,  raising  the  cushion-coat  in  small  places  from  the 
concrete.  It  was  also  found  that  it  would  be  difficult  to  prevent 
the  cushion-coat  from  sliding  on  the  base  and  at  the  same  time  to 
get  a  thorough  bond  between  the  top  and  the  cushion-coat,  so  that 
it  was  deemed  best  to  change  somewhat  the  method  of  construction, 
and  for  the  cushion-coat  to  substitute  a  so-called  binder,  made  up  of 
coarse  stones  held  together  by  asphaltic  cement.  This  binder  has 
been  laid  of  different  thicknesses,  sometimes  1-J  or  even  2  inches. 
Its  object,  however,  is  simply  to  serve  as  a  medium  between  the 
wearing  surface  and  the  concrete.  The  binder  will  take  a  firmer 
hold  upon  the  concrete  than  the  finer  top  surface  would,  and  the 
top  surface  will  form  a  perfect  union  with  the  binder,  so  that  in  this 
way  a  better  result  is  obtained  than  by  the  old  method.  As  the 
province  of  the  binder  is  simply  to  serve  as  this  connecting  link, 
there  seems  to  be  no  necessity  for  making  it  any  thicker  than  what 
is  required  to  make  a  solid  course,  and  the  thickness  of  1  inch 
seems  ample  for  this  purpose. 


ASPHALT  PAVEMENTS.  231 

The  stone  of  which  this  binder  is  composed  should  be  hard, 
angular,  and  somewhat  graded  in  size.  It  should  all  pass  through 
a  screen  of  1-inch  mesh  and  be  retained  by  a  No.  10  screen. 
It  should  be  so  hard  that  it  will  not  break  up  under  the  roller, 
and  should  be  free  from  all  decomposed  or  soft  material.  The 
binder  is  to  be  cemented  by  asphaltic  cement,  but  need  not,  and  in 
fact  should  not,  have  the  voids  filled.  Only  enough  cement  should 
be  used  to  insure  the  holding  together  of  the  stones.  If  too  great 
a  quantity  be  used,  in  a  short  time  it  will  gradually  work  up  into  the 
wearing  surface  and,  by  increasing  the  amount  of  bitumen,  make 
the  pavement  too  soft  and  cause  its  failure.  This  happened  upon 
one  street  in  Brooklyn,  and  the  analysis  of  the  wearing  surface 
showed  an  excess  of  50  per  cent  of  bitumen. 

Foundation. 

Of  whatever  material  the  asphalt  pavement  may  be  made,  or 
with  whatever  care  it  may  be  laid,  it  will  always  be  a  failure  unless 
it  is  laid  on  a  good  foundation.  This  statement  is  true  of  almost 
every  work  of  construction,  but  it  is  particularly  so  of  asphalt,  be- 
cause the  asphalt  itself  simply  acts  as  a  carpet  to  receive  the  traffic, 
but  the  weight  must  be  borne  by  the  foundation.  Asphalt  has  no 
inherent  strength.  It  does  its  work  by  its  elasticity,  simply  trans- 
ferring the  loads  to  the  foundation. 

Mention  has  been  made  of  a  bituminous  base  used  in  the  early 
-days  in  Washington.  In  South  Omaha,  Neb.,  in  1891  an  asphalt 
pavement  was  laid  on  a  bituminous  base  somewhat  differently  con- 
structed than  those  of  Washington.  It  was  made  of  broken  stone 
.and  gravel  6  inches  deep,  and  the  entire  portion  thoroughly  mixed 
with  asphalt  so  that  the  base  itself  was  a  concrete  cemented  by 
asphalt.  Upon  a  good  foundation  this  makes  a  good  base,  but  it 
has  not  much  strength  in  itself,  and  when  the  pavement  comes  to 
be  relaid  it  is  generally  necessary  to  take  up  the  entire  base.  The 
best  base  is  made  of  broken  stone  and  hydraulic  cement  concrete. 
Its  thickness  depends  upon  the  traffic  of  the  street,  but  it  is  almost 
invariably  laid  with  a  depth  of  6  inches.  Some  time  after  the 
success  of  asphalt  pavement  was  fully  assured,  an  attempt  was  made 
to  reduce  its  cost  and  allow  it  to  compete  more  successfully  with 


232        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

other  pavements  by  varying  its  character  and  thickness  according 
to  the  amount  of  traffic.  A  foundation  of  6  inches  of  broken  stone 
was  laid  upon  a  prepared  subgrade  and  thoroughly  rolled.  Upon 
this  was  scattered  coal-tar  in  quantity  approximating  1  gallon  per 
square  yard.  The  asphalt  was  then  laid  upon  -the  stone.  This  base 
is  even  more  objectionable  than  the  one  .spoken  of  in  South  Omaha, 
as  it  has  absolutely  no  strength  in  itself,  will  settle  with  every 
inequality  of  the  ground  upon  which  it  rests,  and  unless  the  sub- 
grade  has  been  made  absolutely  solid  and  compact,  the  surface  of  the 
pavement  must  become  rough  and  uneven.  With  proper  care,  how- 
ever, in  preparing  the  subgrade  and  by  rolling  the  broken  stone  in 
somewhat  the  same  manner  as  is  done  for  macadam  pavements, 
a  foundation  can  be  obtained  which,  if  not  disturbed  by  plumbers 
or  for  any  subsurface  construction,  will  give  good  and  satisfactory 
results,  but  its  cost  in  that  case  would  be  almost  as  great  as  if  laid 
with  hydraulic  cement. 

In  1899  such  a  base  was  being  used  in  some  instances  in  Phila- 
delphia, but  probably  not  in  any  other  city  in  the  country  to  any 
extent. 

When  an  old  stone  pavement  is  being  replaced  with  asphalt,  it 
is  often  desirable  to  lay  the  new  pavement  over  the  old  and  thus, 
save  the  cost  of  a  new  foundation.  This  has  been  done  to  quite  an 
extent  in  many  cities.  Notably  so  in  New  York  and  Brooklyn. 
Many  of  the  old  cobblestone  streets  in  Brooklyn  have  been  covered 
with  asphalt.  There 'would  be  almost  no  objection  to  this  practice 
if  the  street  were  to  remain  undisturbed  by  plumbers,  and  the  old 
pavement  were  laid  with  the  proper  cross-section  desired  for  the 
new,  but  in  almost  every  case  it  is  necessary  to  relay  at  least  one- 
half  and  sometimes  the  whole  of  the  old  cobblestone  in  order  to- 
get  the  desired  cross-section.  This  gives  a  foundation  which  must 
necessarily  be  more  or  less  unstable,  and  when  the  entire  surface 
is  relaid  the  cost  would  be  fully  one-half  that  of  the  hydraulic- 
cement-concrete  foundation.  There  are  also  a  great  many  holes- 
and  inequalities  in  a  cobblestone  pavement  which  must  be  filled  up 
or  repaved.  In  such  a  case,  where  the  old  cross-section  will  admit, 
a  most  satisfactory  result  can  be  obtained  by  filling  in  all  of  the 
inequalities  with  broken  stone  and  rolling  them  to  a  true  surface 
across  the  entire  street  and  laying  the  pavement  upon  it.  Asphalt 


ASPHALT  PAVEMENTS.  23& 

lias  also  been  laid  very  successfully  over  granite  and  Belgian  block 
pavements.  There  has  been  a  great  amount  of  this  work  done  in 
Xew  York  City.  There  the  pavements  in  almost  every  instance 
were  taken  up  and  relaid  at  a  lower  elevation  than  originally,  so- 
as  to  bring  the  surface  of  the  new  pavement  approximately  equal 
to  that  of  the  old.  When  this  is  done  the  blocks  are  laid  with 
quite  open  joints,  filled  to  within  about  1  inch  of  the  top  with, 
sand,  leaving  room  for  the  binder  to  fill  up  the  remainder  and  so 
obtain  a  firm  hold  upon  the  new  surface.  Asphalt  has  also  been 
laid  over  old  macadam  roads,  and  where  the  pavement  is  to  be  un- 
disturbed no  possible  objection  can  be  made  to  this  practice. 

Laying  the  Pavement. 

With  good  materials,  well  mixed,  and  in  proper  proportion,  it 
is  very  easy  to  produce  a  poor  pavement  by  bad  manipulation  and 
inexperienced  workmen  on  the  street.  After  the  foundation,  of 
whatever  nature,  is  ready  for  the  pavement  proper,  the  binder 
should  be  brought  to  the  street  and  spread  to  such  a  depth  (which 
can  easily  be  determined  by  practice)  as  will  give  it  a  thickness  of  1 
inch  after  being  compressed.  If  the  foundation  is  cement  con- 
crete, and  has  not  had  sufficient  time  to  become  thoroughly  set,  it 
should  be  covered  on  one  side  with  planks  for  the  trucks  to  drive 
over,  especially  if  the  blocks  are  long.  It  is  also  often  better,  when 
the  blocks  are  of  extreme  length,  to  begin  laying  the  binder  in  the 
centre  rather  than  at  one  end,  so  that  the  trucks  will  not  be  obliged 
to  drive  over  the  foundation  for  more  than  half  the  length  of  the 
block,  thus  saving,  if  the  planks  are  used,  half  the  amount  of 
material  and  preventing  any  damage  to  the  foundation.  The  same 
rule  will  hold  good  in  laying  the  top,  as,  however  good  the  binder 
may  be,  it  is  liable  to  be  injured  by  too  much  driving  if  the  blocks- 
are  of  extreme  length.  The  laying  of  the  wearing  surface  should 
follow  the  binder  as  quickly  as  possible.  Should  the  weather  be* 
good,  this  is  not  so  essential;  but  in  wet  weather,  or  in  the  latter 
part  of  the  season,  the  binder,  being  porous,  is  liable  to  be  acted" 
upon  by  the  moisture  and  become  brittle  and  disintegrate  under  a 
small  amount  of  traffic  if  it  has  remained  exposed  for  any  appreci- 
able length  of  time.  In  such  weather,  where  possible,  it  is  good 


234        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

practice  to  lay  the  binder  in  the  forenoon  and  cover  it  with  asphalt 
in  the  afternoon,  although  if  the  following  day  should  be  pleasant 
this  would  not  be  actually  necessary. 

In  preparing  for  the  wearing  surface,  a  line  should  be  marked 
along  the  curb  at  the  height  of  the  finished  surface,  so  that  it  can 
always  be  ascertained  whether  a  sufficient  depth  is  obtained.  The 
surface  of  the  concrete  having  been  laid  in  the  same  manner  as  that 
•described  for  stone  pavements,  by  means  of  ordinates,  the  thickness 
of  the  asphalt  at  any  point  on  the  street  can  be  determined  by 
stretching  a  line  from  curb  to  curb  and  measuring  down  at  any 
desired  point. 

The  material  for  the  wearing  surface  should  be  brought  upon 
the  street,  in  carts  protected  from  the  weather,  at  a  temperature  of 
not  less  than  250°;  and  if  the  weather  be  cold,  275°  or  even  300° 
is  preferable.  After  being  dumped  upon  the  binder  it  is  spread  out 
into  its  approximate  depth  by  shovellers,  and  then  graded  off  by 
experienced  workmen  with  rakes.  Several  devices  have  been  used 
for  determining  the  proper  depth  of  the  loose  material,  such  as 
having  rakes  with  teeth  of  a  certain  length,  etc.,  but  after  a 
little  experience,  an  intelligent  laborer  soon  learns  the  required 
depth,  and  easily  tells  by  his  eye  whether  or  not  a  particular 
place  is  too  high  or  too  low.  As  soon  as  the  material  is  spread 
out  to  the  required  depth  by  the  rakers,  it  should  receive  its 
preliminary  compression  by  hand-rollers,  after  which  hydraulic 
cement  should  be  lightly  broomed  over  the  surface  and  then  rolled 
by  a  steam-roller  weighing  about  five  tons.  This  roller  should  be 
followed  in  a  short  time  by  one  weighing  not  less  than  ten  tons,  or 
250  Ibs.  per  inch  of  roller.  The  object  of  the  three  rollers  is  to 
allow  the  asphalt  to  be  compressed  without  being  pushed  forward. 
If  a  heavy  roller  is  used  at  first,  before  the  material  has  had  the 
preliminary  compression,  the  tendency  will  be  in  many  cases  to 
push  the  material  at  times  rather  than  compress  it  vertically,  and 
thus  cause  inequalities  in  the  surface  which  are  very  hard  to  be 
rolled  out.  This  rolling  should  follow  the  distribution  of  the  ma- 
terial closely,  so  that  it  shall  not  have  time  to  cool  before  the  final 
compression  is  obtained.  Some  asphalts  have  a  certain  amount  of 
natural  set  in  themselves,  and  consequently  require  more  care  in 
rolling  than  others;  for  if  this  set  takes  place  before  the  final 


ASPHALT  PAVEMENTS.  235 

compression  is  reached,  no  amount  of  rolling  will  produce  a  true 
and  impervious  surface.  The  state  of  the  weather  also  is  an  element 
to  be  considered.  If  a  strong  wind  be  blowing,  the  material,  spread 
out  as  it  is,  over  a  broad  surface  only  2  or  3  inches  thick,  will  cool 
much  more  rapidly  than  on  a  calm  day  when  the  temperature  is 
considerably  lower.  On  the  other  hand,  when  the  weather  is  hot 
there  is  no  necessity  of  following  up  the  rakers  so  closely.  The  roll- 
ing should  be  continued  without  any  cessation  until  the  asphalt  has 
received  its  ultimate  compression.  If  the  street  be  wide  enough, 
the  rolling  should  be  done  crosswise  as  well  as  lengthwise  on  the 
street,  and  in  any  event  the  rolling  should  be  done  at  as  great  an 
angle  as  possible,  so  that  any  little  inequality  which  might  be  caused 
by  .the  roller  moving  lengthwise  may  be  taken  out  by  this  cross- 
action.  The  amount  of  rolling  required  depends  upon  circum- 
stances greatly,  but  in  general  two  such  rollers  as  above  described 
should  roll  2000  square  yards  of  wearing  surface  in  ten  hours. 
Fig.  14  represents  the  cross-section  of  an  asphalt  pavement. 


FIG.  14. 

When  the  mixture  for  the  wearing  surface  is  dumped  upon  the 
binder  all  lumps  should  be  carefully  broken  up  and  spread  out,  and 
the  material  taken  up  clean  from  where  it  was  dumped  upon  the 
binder,  lest  if  any  appreciable  amount  be  left  it  will  cool  and  be- 
come hard  before  it  is  covered  up  by  the  top,  and  so  not  receive 
the  required  amount  of  compression,  and  eventually  wear  away  and 
fail  at  this  place. 

In  making  the  connection  with  the  pavement  that  has  been  laid 
at  any  appreciable  time  before,  care  should  be  exercised  to  make  a. 
perfect  joint  with  the  old  work  by  heating  the  edge  or  painting  it, 
with  asphaltic  cement.  In  some  asphalts  it  is  necessary  to  cut  the 
joint  down  vertically;  otherwise  if  it  is  chamfered  off,  it  will  after- 
wards scale  under  traffic. 

Where  asphalt  pavement  joins  a  street-car  track,  stone  header, 
or  any 'unyielding  surface,  it  should  be  laid  about  one -eighth  of  an 


236        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

inch  above  it,  as  wheels  coming  from  the  hard  iron  or  stone  to  .the 
softer  asphalt  will  compress  the  latter,  so  that  soon  a  depression 
will  be  formed,  eventually  becoming  a  hole  under  the  blows  from 
the  wheels. 

Gutters. 

In  most  cities  it  is  customary  to  lay  the  asphalt  up  to  the  curb. 
In  such  cases  special  care  should  be  exercised  to  thoroughly  com- 
press the  material  in  the  gutter;  and  as  it  is  often  difficult  to  roll 
this  thoroughly,  it  should  be  tamped  by  hand  with  irons  especially 
prepared  for  this  purpose.  A  straight-edge  some  12  or  14  feet  long 
should  be  used,  so  that  the  -gutter  may  conform  to  the  exact  grade 
of  the  curb  and  be  free  from  any  slight  depression.  For  a  distance 
of  12  inches  from  the  curb  the  surface  should  be  painted  with 
asphaltic  cement  and  ironed  in  with  hot  smoothing-irons.  This 
should  be  done  immediately  after  the  tamping,  before  any  foreign 
matter  has  gathered  upon  it  and  when  the  pores  are  comparatively 
open.  The  object  of  this  is  to  saturate  the  material  thoroughly 
•with  asphalt  and  prevent  any  subsequent  absorption  of  moisture 
which  would  lead  to  disintegration.  The  smoothing-irons  used 
should  not  be  too  hot.  Iron  does  not  show  any  heat  by  color  until 
it  is  at  a  temperature  of  about  1000°  or  1200°  Fahr.,  and  this 
temperature  would  be  detrimental  to  the  asphalt  and  liable  to  burn 
it  sufficiently  to  cause  disintegration. 

It  is  claimed  by  advocates  of  Bermudez  and  Alcatraz  asphalts 
that  the  water  does  not  injure  either  material,  and  for  that  reason 
this  work  is  not  necessary;  but  at  the  present  time  it  is  customary 
to  treat  all  asphalts  in  this  manner  where  the  material  is  laid  from 
curb  to  curb.  On  account  of  this  effect  of  the  water,  however, 
stone,  brick,  and  sometimes  cement  are  used  for  gutters  in  some 
cities.  In  the  city  of  Washington  the  officials  have  decided  to  use 
vitrified  paving-brick  for  this  purpose.  This  material  has  been  in 
use  there  for  some  years,  and  has  given  satisfaction,  as  it  presents  a 
smooth  surface  to  traffic-  and  is  not  acted  upon  by  the  water.  Where 
either  stone  or  brick  is  used,  the  concrete  should  be  depressed 
sufficiently  so  that  it  shall  have  the  same  amount  under  the  gutter 
as  under  the  pavement  proper,  and  the  blocks  should  be  set  in 
mortar  on  the  concrete,  not  on  the  cushion  of  sand,  so  that  they 


ASPHALT  PAVEMENTS.  237 

shall  be  perfectly  rigid,  and  the  joints  poured  either  with  Portland- 
•cement  grout  or  asphaltic  cement. 

Temperature  for  Laying. 

It  has  long  been  a  mooted  question  at  what  temperatures  the 
laying  of  sheet  asphalt  should  be  discontinued.  Where  it  is  not 
definitely  stated  in  specifications,  it  is  generally  stipulated  that  it 
shall  cease  at  a  temperature  below  freezing,  but  this  is  very  seldom 
done  in  actual  practice.  It  is  certain  that  better  results  can  be 
obtained  by  laying  the  asphalt  in  warm  weather  than  in  cold,  as 
a  more  perfect  anc1  even  compression  can  be  obtained.  That  this 
is  important  was  demonstrated  on  a  street  where  the  work  was  com- 
pleted at  a  low  temperature  and  opened  for  traffic.  It  soon  began 
to  pick  up  under  the  impact  of  the  horses'  feet,  and  quite  a  portion 
of  it  had  to  be  repaired,  and  at  one  time  it  looked  as  if  an  entire 
"block  would  require  relaying.  Eventually  the  weather  grew  warm 
again,  and  in  a  few  days  the  action  of  the  traffic  had  obliterated  all 
signs  of  the  picking  up,  and  the  compression  required  was  obtained 
by  travel,  and  no  further  trouble  occurred  from  that  source. 

In  another  instance,  a  street  containing  some  12,000  yards  was 
surfaced  at  a  temperature  of  about  zero  where  the  haul  from  the 
plant  was  about  1J  miles.  Nearly  half  of  the  work  was  performed 
under  these  conditions.  The  street  picked  up  considerably  under 
travel  during  the  winter,  and  the  indications  were  that  quite  a 
portion  of  it  would  require  to  be  resurfaced  in  the  spring;  but 
fortunately  there  was  only  slight  travel  on  the  street  during  the 
winter-time,  so  that  not  much  damage  was  done,  and  the  traffic 
during  the  coming  summer  put  the  street  in  such  a  condition  that 
only  about  $500  was  expended  upon  it  during  the  guarantee  period 
of  five  years.  The  practice  of  doing  work  under  these  conditions, 
however,  is  not  to  be  commended,  as  it  is  in  exceptional  cases  only 
that  good  results  are  obtained. 

In  order  to  be  sure  of  good  work,  the  wearing  surface  should 

not  be  laid  at  a  temperature  below  20°. 

• 

Cracks. 

One  of  the  principal  ways  in  which  asphalt  pavement  has  failed 
in  cities  subjected  to  great  extremes  of  temperature  is  by  the  form- 


238        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

ing  of  cracks.  These  are  thought  by  some  engineers  to  be  caused 
by  the  pavement  cracking  through  the  base,  but  a  careful  study  of 
the  subject  does  not  seem  to  bear  out  this  view.  In  one  instance  a 
pavement  laid  in  one.  of  the  Southern  cities  was  subjected  soon 
after  completion  to  a  rapid  change  of  temperature  of  about  40% 
but  even  then  it  was  but  little  below  the  freezing-point,  and  not 
enough  to  cause  any  contraction  in  the  concrete  base,  but  the 
asphalt  surface  showed  a  great  many  fine  cracks,  demonstrating 
conclusively  that  these  cracks  were  formed  in  that  particular  in- 
stance, at  any  rate,  by  the  contraction  of  the  wearing  surface  itself. 
Many  specifications  in  detailing 'how  the  wearing  surface  should 
be  laid  say  that  the  material  shall  be  such  as  to  form,  a  pavement 
which  shall  not  be  too  soft  in  the  summer,  nor  crack  and  disin-, 
tegrate  in-  the  winter.  This  is  a  simple  proposition  in  the  specifi- 
cations, but  not  so  easy  to  carry  out.  The  engineer  generally  wishes. 
a  pavement  to  be  laid  as  hard  as  possible  without  cracking.  The 
contractor,  on  the  other  hand,  has  as  his  standard  one  that  will  be 
as  soft  as  possible  and  not  mark  or  rut  too  much  in  hot. weather.  It 
is  well  known  that  a  pavement  hardens  as  the  volatile- oils  evaporate 
and  the  asphalt  becomes  oxidized,  so  that  the  softer  the  pavement 
is  laid  the  longer  it  will  probably  last,  and  the  aim  of  the  con- 
tractor is  to  lay  it  as  soft  as  possible  without  bad  results  the  first 
season.  Very  frequently  complaints  are  made  of  new  pavements 
cutting  up  and  becoming  rough  under  the  action  of  travel  when 
laid  in  hot  weather,  which  after  the  first  summer  give  no  trouble 
whatever.  As  material  is  laid  soft  and  in  hot  weather,  allowance 
must  be  made  for  the  changing  temperature  to  come,  and  to  meet 
this  successfully  the  skill  of  the  contractor  is  taxed.  A  pavement 
that  is  laid  soft  will  seldom  give  trouble  by  cracking  except  after 
it  has  been  laid  a  long  time.  In  Western  and  Northern  cities, 
where  the  range  of  temperature  is  great,  it  is  probably  impossible 
to  lay  sheet-asphalt  pavements  that  will  not  crack  in  extremely 
cold  weather.  In  the  vicinity  of  New  York  City  very  little  trouble 
is  experienced  by  cracking.  In  some  cities  engineers  have  sought 
to  remedy  this  trouble  by  making  an  expansion- joint  crosswise  of 
the  street  at  frequent  intervals.  The  theory  of  the  expansion- joint 
in  any  structure  is  that  the  material  is  free  to  slide  upon  the  base 
upon  which  it  rests.  This  is  certainly  not  true  of  a  well-constructed 


ASPHALT  PAVEMENTS.  239 

asphalt  pavement,  as  it  is  hardly  conceivable  that  a  binder  with 
this  superimposed  pavement  could  slide  any  appreciable  distance 
on  the  concrete.  An  expansion-joint  will  certainly  cause  a  crack 
to  form,  wherever  it  is  made,  at  a  change  in  temperature,  while 
really  the  contraction  of  the  material  might  be  entirely  taken  up 
by  the  elasticity  of  the  asphalt.  At  all  events,  the  most  that  it 
could  accomplish  would  be  the  formation  of  the  cracks  at  regular 
intervals,  which  is  neither  desirable  nor  of  any  particular  advan- 
tage. 

These  cracks  form  sometimes  from  the  centre  towards  the  gutter 
and  sometimes  from  the  gutter  towards  the  centre,  but  always  in 
the  line  of  the  least  resistance.  As  the  pavement  becomes  older 
more  cracks,  appear  diagonally  and  lengthwise  of  the  street,  dividing 
the  pavement  into  irregular  areas.  When  these  become  small  and 
the  cracks  large  the  pavement  must  be  relaid.  These  cracks  often 
appear  in  a  pavement  without  doing  any  particular  amount  of 
damage,  especially  if  there  is  considerable  traffic  on  the  street.  If, 
however,  there  is  not  traffic  enough  to  consolidate  the  pavement 
after  the  weather  becomes  warm,  the  moisture  enters  the  cracks 
and  hastens  disintegration.  The  best  method  of  taking  care  of 
the  cracks  is  to  prevent  them,  or  where  not  possible  to  do  that 
entirely,  to  devise,  by  a  study  of  the  conditions,  a  composition  that 
will  withstand  changes  of  temperature  to  the  best  advantage. 

If  a  pavement  is  laid  too  soft  and  the  traffic  is  heavy,  the 
result  is  that  an  uneven  surface  soon  forms,  the  top  pushes  under 
traffic,  either  upon  itself  or  upon  the  binder,  or  the  whole  upon 
the  concrete,  and  holes  appear  long  before  they  should  in  such 
cases,  and  the  soft  surface  must  be  taken  up  and  relaid  with  harder 
material.  This  trouble  may  be  caused  by  too  much  flux  in  the 
asphalt  cement,  or  by  an  excess  of  bitumen  being  used  in  the  wear- 
ing surface. 

Effect  of  Illuminating-gas. 

The  action  of  illuminating  gas,  as  it  sometimes  escapes  from 
leaky  mains,  is  very  detrimental  to  asphalt  pavements.  Pavements 
have  failed  in  many  instances  from  causes  for  which  no  explanation 
could  be  given  at  first,  and  the  surface  was  relaid  without  any 
question;  but  in  one  instance  the  pavement  failed  so  frequently 


240        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

that  a  careful  examination  was  made  and  the  odor  of  gas  detected, 
and  when  the  asphalt  was  all  taken  up  sufficient  gas  was  found  to 
give  a  perceptible  flame  when  lighted,  although  the  base  was  6 
inches  of  cement  concrete.  An  examination  of  the  gas-main  at  this 
point  disclosed  a  large  leak.  In  other  cases  also  when  this  failure 
has  been  noticed  broken  gas-mains  'have  been  discovered. 

The  action  of  gas  is  generally  made  manifest  by  the  appearance 
of  a  great  many  cracks  or  checks  in  the  pavement,  lengthwise  of 
the  street,  which  under  traffic  soon  become  soft  and  the  pavement 
disintegrates.  Whether  the  gas  companies  shall  make  such  failure 
good,  whether  they  shall  be  repaired  by  the  contractor  who  has  the 
pavement  under  guarantee,  or  whether  the  expense  shall  be  borne 
entirely  by  the  city,  is  an  interesting  problem,  but  one  which  has 
not  been  satisfactorily  solved  at  the  present  time. 

Damage  by  Fires. 

Another  cause  of  damage  to  asphalt  pavements  is  the  building 
of  fires  upon  them.  While  this  should  never  happen,  as  a  matter 
of  fact  it  does,  and  from  the  report  of  the  water-purveyor  of  New 
York  City  it  is  seen  that  during  the  year  1896  alone  8654  square 
yards  of  asphalt  were  destroyed  by  fire,  at  an  expense  to  the  city 
of  over  $30,000.  In  1894  the  asphalt  so  destroyed  amounted  to 
3410  square  yards,  and  in  1895  to  3692  square  yards.  The  probable 
reason  for  the  excess  in  1896  was  the  fact  that  it  was  a  presidential 
year,  and  the  youth  of  New  York  consider  it  proper  to  celebrate 
the  victory  by  building  bonfires  upon  the  pavement,  without  re- 
gard to  its  effect. 

Standard  for  Condition  of  Street  at  End  of  Guarantee  Period. 

In  the  early  contracts  for  asphalt  pavements  there  was  in- 
serted a  clause  requiring  the  streets  to  be  kept  in  good  repair  for 
a  term  of  years,  and  turned  over  to  the  city  in  such  condition  at 
the  end  of  the  specified  time.  The  words  "  good  repair  "  are  in- 
definite, liable  to  mean  one  thing  to  the  engineer  and  something 
else  to  the  contractor.  So  much  controversy  has  arisen  over  this 
point  that  present  specifications  attempt  to  make  clear  what  is 
expected  and*  required.  Specifications  for  asphalt  pavement  in 
New  York  City  contain  the  following  clause: 


ASPHALT  PAVEMENTS. 

"  Just  previous  to  the  expiration  of  the  guarantee  period  the 
entire  work  shall  be  inspected,  and  any  bunches,,  depressions,  or 
unevenness  in  the  surface  of  the  pavement  that  shall  show  a  varia- 
tion of  §  of  an  inch  under  a  four-foot  straight  edge  or  template, 
or  any  crack  wider  than  J  of  an  inch,  or  any  portion  of  the  pave- 
ment having  a  thickness  of  less  than  1^  inches,  shall  be  immedi- 
ately repaired  upon  the  order  of  the  Commissioner  of  Highways 
by  the  heater  process,  or  by  removing  the  entire  pavement  from  the 
concrete  and  replacing  it  in  the  same  manner  as  when  originally 
laid,  provided  that  when  more  than  50  per  cent  of  the  surface  of 
any  one  block  requires  repairing  according  to  the  above  conditions, 
the  entire  block  shall  be  taken  up  and  relaid.  When  any  defects 
are  caused  by  the  failure  of  the  concrete  the  entire  pavement,  in- 
cluding foundation,  shall  be  taken  up  and  relaid  in  accordance  with 
the  specifications." 

Rock  Asphalt. 

The  rock  asphalts  of  Europe  have  been  made  entirely  of 
bituminous  limestone.  Generally  the  stone  had  become  impreg- 
nated in  some  manner  with  bitumen  so  that  it  became  almost  one 
substance.  Some  bituminous  limestone  has  been  found  in  this  coun- 
try, as  well  as  a  sandstone  bearing  asphalt,  and  also  in  California 
beds  of  sand  which  contained  asphalt,  and  of  which  many  of  the 
early  California  asphalt  pavements  were  made.  These  pavements 
were  laid  in  a  very  crude  manner,  with  but  little  knowledge  of  the 
material  or  the  subject,  and  a  great  many  of  them  failed  in  a  short 
time,  as  might  have  been  expected.  These  failures,  however,  should 
not  have  been  charged  up  to  California  asphalt  or  to  asphalt  pave- 
ments, as  experience  has  demonstrated  that  with  the  proper  treat- 
ment a  good  pavement  can  be  laid  of  this  material. 

Buffalo,  N.  Y.,  probably  has  more  rock  asphalt  pavement  than 
any  other  city  in  the  United  States;  some  of  it  has  been  laid  with 
imported  foreign  asphalt,  and  quite  a  large  amount  by  a  combina- 
tion of  the  foreign  with  the  Kentucky  rock  asphalt.  The  first 
Kentucky  rock  pavement  was  laid  In  Buffalo  in  1890  as  a  sample, 
since  which  time  nearly  10  miles  have  been  laid.  Successful  pave- 
ments have  been  laid  with  an  asphaltic  sand  rock  of  Indian  Terri- 
tory, although  they  have  not  been  developed  to  such  an  extent  as 
the  Kentucky  asphalt.  ^ 


242        STREET  PAVEMENTS  AND  PA  VINO  MATERIALS. 

Wearing  Surface  of  American  Rock  Asphalt  as  used  in 
St.  Louis,  Mo. 

Upon  the  foundation  thus  formed  shall  be  placed  a  wearing 
surface  as  follows: 

A  mixture  of  American  bituminous  rock,  which  shall  be  pre- 
pared and  laid  on  said  concrete  foundation  as  follows:  The  wear- 
ing surface  shall  be  composed  of  bituminous  sandrock  from  the 
Chickasaw  Nation  or  Breckinridge  County,,  Ky.,  50  per  cent  to  66f 
per  cent;  bituminous  limerock  from  the  Buckhorn  mines  in  the 
Chickasaw  Nation,  33^  per  cent  to  50  per  cent.  The  rock  of  both 
materials  shall  be  ground  finely  and  thoroughly  mixed,  and  nothing 
shall  be  added  to  or  taken  from  the  powder  obtained  by  grinding 
the  bituminous  rock.  This  powder  shall  be  heated  in  a  suitable 
apparatus  to  a  temperature  of  from  150°  to  200°  Fahr.;  it  shall 
be  brought  to  the  street  in  suitable  carts,  and  spread  with  rakes  to 
an  even  thickness  of  such  depth  as  will  insure  a  uniform  thickness, 
of  2  inches  after  having  received  its  ultimate  compression.  The 
surface  shall  then  be  compressed  by  tamping  and  rolling,  after 
which  a  small  amount  of  hydraulic  cement  will  be  swept  over  it, 
and  then  it  will  be  thoroughly  compressed  by  a  steam-roller  weigh- 
ing not  less  than  five  tons. 

Method  of  Laying. 

The  bituminous  sandrock  shall  contain  from  9  per  cent  to  12 
per  cent  of  pure  bitumen.  The  bituminous  limerock  shall  be  as 
nearly  as  possible  a  pure  carbonate,  thoroughly  and  evenly  impreg- 
nated with  asphalt,  having  no  more  impurities  than  the  standard 
German  rock  asphalt  of  Limmer  or  Vorwhole,  and  shall  contain  not 
less  than  7  per  cent  and  not  more  than  12  per  cent  of  bitumen, 
according  to  the  richness  of  the  bituminous  sand  used. 

The  method  of  laying  the  European  rock  asphalt  is  entirely 
different  from  that  of  the  ordinary  sheet  asphalt.  The  material 
is  taken  from  the  mines  and  shipped  to  the  city  where  it  is  to  be 
used  in  its  natural  state.  The  products  of  the  foreign  mines  vary 
in  the  amount  of  bitumen  contained,  some  having  too  little  and 
others  too  much,  so  that  it  is  generally  necessary  to  mix  the  dif- 
ferent products  so  as  to  get  the  required  amount  of  bitumen  in 
the  pavement,  which  is  approximately  10  per  cent.  . 

After  these  proportions  have  been  determined  and  the  material 


ASPHALT  PAVEMENTS.  243 

mixed,  it  is  first  crushed  with  rollers  at  the  plant  and  then  reduced 
to  a  fine  powder  by  being  passed  through  disintegrators,  after 
which  it  is  sifted  through  a  sieve  to  separate  any  lumps  that  might 
otherwise  get  into  the  pavement.  This  powder  is  then  heated  in 
a  cylinder  which  is  kept  constantly  in  motion  to  allow  the  air  to 
circulate  freely  among  the  particles,  and  kept  for  about  two  hours 
at  a  temperature  from  300°  to  325°  Fahr.  The  material  is  then 
carried  in  carts  to  the  street  and  spread  upon  the  prepared  base  to 
a  depth  that  will  give  the  required  thickness  when  thoroughly  com- 
pacted. 

The  binder  course  is  not  generally  used  with  rock  asphalt,  al- 
though it  is  sometimes.  Over  the  powder  spread  upon  the  street 
a  light  roller  is  run  to  give  the  surface  its  initial  compression,  when 
workmen,  each  with  a  round  iron  rammer  some  G  or  7  inches  in 
diameter,  carefully  go  over  the  surface,  one  following  the  other, 
all  striking  blows,  in  unison,  on  the  asphalt  until  it  is  thoroughly 
compacted.  A  coat  of  hydraulic  cement  is  then  spread  over  the 
surface,  when  it  is  ready  for  the  final  rolling,  which  should  be  done 
by  steam,  and  preferably  with  an  arrangement  inside  the  roller  for 
keeping  it  hot.  About  twelve  hours  after  the  rolling  is  completed 
and  the  material  has  become  cold,  the  street  can  be  thrown  open  to 
travel,  which  continually  adds  to  the  compression  already  given. 
It  has  been  found  in  several  instances,  where  a  pavement  has  been 
laid  and  subjected  to  heavy  traffic  for  a  number  of  years,  that  while 
it  has  decreased  very  materially  in  thickness,  its  weight  has  not 
correspondingly  decreased,  showing  that  compression  has  been 
continually  going  on.  Eock  asphalt  very  seldom  gives  any  trouble 
by  cracking. 

In  a  report  upon  rock  asphalt  pavements  made  to  the  corpora- 
tion in  1900,  the  City  Engineer  of  London  names  sixteen  streets 
that  were  relaid  at  the  end  of  the  guarantee  period.  The  original 
contract  provided  for  free  maintenance  for  two  years  and  a  specified 
sum  for  <the  fifteen  years  next  following,  making  a  total  life  of 
seventeen  years.  The  following  streets  lasted  longer: 

Years. 

The  Poultry 19 

London- Wall 20 

Princess  Street 22 

Lothbury 23 

Mansion  House  Street. .  28 


244        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

The  cost  of  maintaining  these  streets  after  the  first  two  years 
was  from  12^  to  37 J  cents  per  yard  per  year,  the  average  being 
20  cents.  To  quote  from  his  report: 

"  In  nearly  all  of  the  main  streets  of  the  city  which  have  been 
paved  with  compressed  asphalt,  it  has  remained  down  during  the 
contract  term  without  an  entire  relay,  and  in  some  instances,  in 
minor  streets  with  small  traffic  where  the  contract  term  of  main- 
tenance has  been  extended,  the  pavements  have  been  down  for 
nearly  thirty  years." 

Repairs  and  Maintenance. 

It  is  extremely  difficult  to  ascertain  just  what  the  expense 
has  been  to  different  municipalities  for  keeping  in  repair  their 
asphalt  pavements.  First,  because  these  pavements  are  laid  with 
the  condition  that  the  contractor  guarantees  them  and  keeps  them 
in  repair  for  a  period  of  at  least  five  years  and  sometimes  ten  and 
even  fifteen  years.  This  practice  arose  from  the  hesitation  of  all 
cities  to  adopt  an  untried  material  like  asphalt  for  street  pavement 
without  a  guarantee  that  they  should  be  freed  from  any  cost  of 
repairs  for  at  least  that  time.  Consequently  it  is  impossible  to  get 
any  information  of  the  repairs  for  the  first  five  years. 

Second,  because  the  proper  method  of  taking  care  of  the  streets 
after  the  guarantee  period  had  expired  is  a  question  of  great  im- 
portance to  all  cities  which  had  adopted  this  pavement,  and  has 
not  yet  been  definitely  determined.  The  asphalt  industry  was 
in  the  hands  of  a  few  people,  and  they  only  were  capable  of  under- 
taking any  repairs.  The  plan  adopted  by  Omaha,  Neb.,  in  1888, 
when  the  first  pavement  laid  there  reached  the  end  of  the  guarantee 
period,  was  to  make  a  contract  with  the  paving  company  to  keep 
all  of  the  pavement  thus  laid  in  repair  for  an  additional  ten  years  for 
8  cents  per  yard  per  annum  for  the  entire  area  of  the  pavement, 
no  matter  how  much  was  actually  relaid.  While  this  gives  the 
exact  cost  to  the  city,  it  does  not  give  any  indication  of  what  the 
actual  expense  was  to  the  contractors.  At  that  time  no  asphalt 
pavement  had  been  laid  fifteen  years  in  this  country,  and  no  one 
could  tell  what  its  condition  would  be  at  the  end  of  that  time,  so 
that  any  figures  as  to  the  cost  of  the  repairs  of  the  same  could  be 
no-thing  but  a  guess.  Without  doubt  on  certain  of  the  heavy-traffic 


ASPHALT  PAVEMENTS.  245 

streets  of  Omaha  the  expense  for  repairs  for  that  period  was  more 
than  the  sum  received;  but  on  others,  where  the  traffic  was  less, 
the  cost  of  repairs  was  correspondingly  less. 

The  objection  to  this  method  is  that,  no  matter  how  well  the 
pavement  may  be  laid,  or  how  little  travel  there  may  be,  it  will  cost 
just  as  much  for  repairs  as  the  pavement  on  a  heavy-traffic  street. 
Its  advantage  is  an  exact  knowledge  of  what  the  pavement  will  cost 
for  a  specified  term  of  years. 

In  Cincinnati  a  method  somewhat  similar  to  this  has  been 
adopted,  except  that  the  bids  have  been  taken  for  a  term  of  years 
upon  each  street,  so  that  it  is  possible  to  separate  the  cost  to  a  cer- 
tain extent  on  the  streets  of  different  traffic,  or  rather  the  con- 
tractor's estimate  of  what  these  different  costs  will  amount  to  in 
a  given  time.  On  the  Cincinnati  streets  laid  in  this  manner  the 
cost  has  averaged,  for  the  first  term  of  five  years  after  the  expira- 
tion of  guarantee,  7£  cents,  although  on  some  of  the  streets  the 
cost  has  been  very  much  more. 

A  much  better  and  more  intelligent  method  has  been  adopted 
by  Buffalo.  There  the  city  receives  bids  for  repairing  streets,  the 
contractor  specifying  the  price  per  square  yard  for  actual  work 
performed,  making  one  price  for  "  skimming  work,"  as  it  is  called, 
and  another  for  repaving  complete.  In  1897  the  price  for  skimming 
was  98  cents,  and  for  repaving  $1.46,  while  in  1898  the  prices  were 
64  cents  and  $1.05  respectively. 

Skimming,  as  it  is  called,  is  a  method  of  repairing  the  surface 
of  the  pavement  by  heating  the  asphalt  with  a  patented  apparatus, 
so  that  the  old  inert  matter  can  be  easily  scraped  off  and  new  live 
material  added  and  rolled  so  as  to  form  a  complete  junction  with 
the  old.  This  has  been  in  use  for  several  years,  and  has  given 
satisfaction  in  materially  reducing  the  cost  of  repairs  over  the 
old  method,  when  it  was  necessary  to  cut  out  the  entire  pavement 
in  every  case.  The  objection  to  the  Buffalo  method  of  paying 
for  repairs  is  that,  as  all  patches  are  guaranteed  for  a  period  of  five 
years,  it  is  necessary  to  locate  them  definitely,  which  entails  a  vast 
amount  of  labor  and  complication,  as  in  the  course  of  five  years  the 
patches  are  apt  to  lap  and  overlap  several  times.  If  a  guarantee  of 
'  five  .years  is  not  exacted,  a  thorough  knowledge  of  the  material  and 
method  of  laying  must  be  had  by  the  city  authorities. 


246        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


In  Washington  still  another  method  is  in  use  for  paying  for 
repairs.  There  a  price  is  paid  in  bulk  for  the  material  used,  meas- 
ured in  carts.  In  1897  the  cost  was  95  cents  per  cubic  foot  for 
skimming  work,  and  52  cents  per  cubic  foot,  where  the  old  material 
was  all  removed,  for  wearing  surface,  and  30  cents  per  cubic  foot 
for  binder.  This  is  probably  the  best  method  of  all,  provided  that 
competent  inspectors  can  be  had  of  the  material  and  method  of 
laying,  as  in  this  way  the  city  pays  for  the  actual  amount  of  ma- 
terial used,  and  consequently  the  contractor  can  bid  intelligently, 
knowing  that  he  will  be  paid  for  what  work  he  actually  does.  In 
this  way,  as  well  as  by  the  Buffalo  plan,  the  amount  of  repairs  can 
be  ordered  by  the  city  and  carried  out  without  any  friction  on  the 
part  of  the  contractor.  By  the  Omaha  and  Cincinnati  methods 
disputes  are  liable  to  and  often  do  arise  as  to  the  exact  amount  of 
surface  to  be  relaid.  In  these  four  cities  more  definite  figures  have 
been  obtained  as  to  the  actual  cost  to  the  city  for  repairs  than  in 
any  other  places  in  the  United  States. 

Table  No.  63  shows  the  average  annual  cost  per  yard  for  re- 
pairs after  the  expiration  of  guarantee  at  the  end  of  different 
periods.  That  is,  all  pavements  after  they  have  been  out  of  guar- 
antee from  one  to  seventeen  years  had  cost  on  an  average  the 

TABLE  No.  63. 


Year  out  of 
Guarantee. 

Washington. 

Buffalo. 

Cincinnati. 

Omaha. 

1 
2 
3 

$0.0004 
.0015 

$0.0132 
.0234 
.0229 

$0.075 
.075 
.075 

$0.08 
.08 
.08 

4 

0391 

.075 

.08 

5 

6 

7 
8 
9 
10 
11 

.007 
.014 
.036 
.045 
.044 
.048 
.038 

.0521 
.0916 
.0749 
.0502 
.0691 
.0219 
.0200 

.075 
.0858 
.0936 
.0994 
.1039 
.1075 

.08 
.08 
.08 
.08 
.08 
.08 
.0754 

12 

023 

0280 

13 

074 

.0415 

14 

.122 

15 

.077 

16 

17 

024 

ASPHALT  PAVEMENTS. 


247 


TABLE  No.  64. 

SHOWING  THE  AVERAGE  COST   PER  YARD  FOR  EACH  YEAR  AFTER 
GUARANTEE   HAS   EXPIRED. 


Year  out  of 
Guarantee. 

Washington. 

Buffalo. 

Cincinnati. 

Omaha. 

1 

.0039 

.029 

.075 

.08 

2 

.0074 

.057 

.075 

.08 

3 

.045 

.051 

.075 

.08 

4 

.034 

.095 

.075 

.08 

5 

.054 

.074 

.075 

.08 

6 

.057 

.084 

.140 

.08 

7 

.068 

.056 

.140 

.08 

8 

.086 

.042 

.140 

.08 

9 

.072 

.027 

.140 

.08 

10 

.080 

.031 

.140 

.08 

H 

035 

040 

03  ± 

12 

031 

106 

13 

.033 

14 

026 

15 

025 

16 

.128 

17 

.031 

amount  opposite  the  year  out  of  guarantee,  while  Table  No.  64 
shows  the  average  cost  per  yard  for  each  year  after  the  guarantee 
has  expired,  the  figures  representing  the  average  of  all  pavements 
during  the  first,  second,  and  third  years  out  of  guarantee  respect- 
ively, being  made  up  for  Washington  and  Buffalo  from  1897 
reports,  and  by  personal  inquiry  from  Cincinnati  and  Omaha.  The 
original  guarantee  in  every  case  was  five  years,  except  upon  streets 
paved  in  Buffalo  in  1884,  when  it  was  eight  years.  It  will  be  seen 
in  the  Omaha  figures  that  the  repairs  for  the  eleventh  year  out  of 
guarantee  cost  only  3  cents,  while  for  all  other  years  they  cost  8 
cents.  This  figure  of  3  cents  referred  to  one  street  only,  but  it  was 
the  first  street  paved  with  asphalt  west  of  Chicago,  if  not  west  of 
Ohio.  It  is  possible,  too,  that  the  street  might  have  been  left  in 
«uch  good  condition  at  the  end  of  this  guarantee  that  it  required 
but  little  repairs  the  following  year,  as  it  is  impossible  for  any  one 
to  tell  by  examination  of  the  asphalt  what  its  economical  condition 
is  as  regards  repairs  without  the  entire  history  of  the  pavement  and 
its  maintenance  cost. 

The  average  cost  per  yard  of  all  asphalt  maintained  in  Buffalo 


248        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

has  been:    for  1895,  $0.067;    1896,  $0.0439;    1897,  $0.0480;    and 
1898,  $0.0288. 

The  Chief  Engineer  of  Buffalo,  in  his  report  for  the  year  ending 
December  31,  1898,  submitted  a  list  of  asphalt  streets  that  he 
recommended  be  repaved,  as  they  had  cost  on  an  average  from 
$0.0558  to  $0.30  per  yard  per  year  for  repairs.  Only  2f  per  cent 
of  the  entire  pavement  under  maintenance  required  repairing  in 
1898,  as  against  5J  per  cent  in  1895. 

In  Kochester,  N.  Y.,  the  cost  of  maintaining  300,000  square 
yards  of  asphalt  pavement  in  1898  was  $0.004  per  yard. 

In  some  of  the  Denver,  Colo.,  specifications  a  proposition  was 
made  for  making  a  contract  for  repairs  for  an  additional  ten  years 
after  the  expiration  of  the  guarantee  period,  at  a  cost  not  to  ex- 
ceed 10  cents  per  yard  per  year.  In  recent  specifications  of  Newark^ 
N..  J.,  the  city  agreed  to  pay  the  contractor  5  cents  per  yard  per  year 
for  the  ten  years  following  the  five-year  guarantee. 

European  pavements  have  cost  considerably  more  than  those  of 
the  United  States.  This  is  attributable  principally  to  the  increased 
traffic.  The  average  cost  of  maintenance  per  square  yard  in  Paris 
for  1893  was  37  cents.  In  Berlin  it  was  10  cents  per  yard  per  year  for 
a  period  of  fifteen  years  after  the  guarantee  period  had  expired,  and 
on  railroad  streets  15  cents  for  space  between  tracks  and  for  a  dis- 
tance of  27£  inches  outside.  In  London  in  1882  the  average  cost 
of  twenty-eight  streets  was  21  cents  per  yard.  In  Glasgow  a  sink- 
ing fund  of  10  per  cent  is  provided  in  the  case  of  asphalt  for  main- 
tenance and  repairs.  In  Leith,  Scotland,  one  asphalt  street  cost 
5  cents  per  yard  per  year  for  fifteen  years  following  the  third  year 
after  being  laid. 

Noiseless  Manhole  Covers. 

On  streets  paved  with  asphalt,  where  sewer  manholes  occur  at 
frequent  intervals,  complaints  have  often  been  made  of  the  noise 
caused  by  the  wheels  of  vehicles  running  from  the  asphalt  over  the 
iron  manhole-cover.  To  obviate  this  trouble  a  cover  shown  in 
Fig.  15  has  been  used  successfully  in  Brooklyn. 

The  covers  are  taken  to  the  contractors'  yard  and  then  filled 
with  the  asphalt  mixture,  when  they  are  distributed  on  the  different 
streets  as  may  be  desired. 


ASPHALT  PAVEMENTS. 


249 


UNDER  SIDE  OF  COVER. 
FIG.  15. 


Cost  of  Asphalt  Pavements. 

It  is  difficult  to  make  an  estimate  of  the  cost  of  a  sheet-asphalt 
pavement. 

The  price  of  the  different  kinds  of  material  varies,  as  well  as 
the  quantities  used  per  square  yard. 

tools  and  machinery  used  for  laying  and  mixing  are  ex- 


250        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

pensive  and  involve  the  expenditure  of  a  large  sum  of  money,  the 
interest  on  which  and  the  depreciation  of  the  plant  varying  the 
price  per  yard  according  to  the  amount  of  pavement  laid  in  any 
one  year. 

There  are  also  many  other  charges,  such  as  labor,  superin- 
tendence, etc.,  that  could  not  be  accurately  determined  without 
access  to  the  books  of  the  contractor. 

Assuming  a  square  yard  of  wearing  surface  to  weigh  90  pounds 
per  inch  of  depth,  and  knowing  the  percentage  of  bitumen  required 
in  the  pavement,  as  well  as  the  amount  contained  in  the  asphalt, 
the  pounds  of  asphalt  per  square  yard  of  surface  can  be  easily  cal- 
culated. Its  quantity  must  vary  greatly  when  asphalts  containing 
from  55  to  90  per  cent  of  bitumen  are  used. 

Of  80  per  cent  asphaltic  cement  20J  pounds  will  lay  a  square 
yard  of  wearing  surface  2  inches  thick,  which  will  analyze  about  9 
per  cent  bitumen;  always  remembering  that  if  petroleum  is  used 
for  a  flux,  practically  all  of  it  will  be  soluble  in  carbon  bisulphide 
and  consequently  will  rank  as  bitumen. 

In  Brooklyn,  N.  Y.,  asphalt  pavements  consisting  of  2  inches 
of  wearing  surface  and  1  inch  of  binoler  were  laid  for  80  cents  per 
square  yard. 

This  price,  however,  was  the  result  of  keen  competition  and 
cannot  be  taken  as  a  guide  to  the  actual  cost. 

Cost  of  Asphalt. 

In  a  trade  pamphlet  issued  a  few  years  ago  by  the  Standard 
Asphalt  Co.,  California  asphalt  containing  90  per  cent  bitumen 
was  offered  in  New  York  for  $32  per  ton  shipped  by  rail,  and 
$26.50  via  Cape  Horn  on  sailing  vessels.  The  cost  was  determined 
by  a  fixed  price  of  $17.50  per  ton  at  Asphalto,  Cal. 

Asphalt  from  Los  Angeles,  Cal.,  was  offered  in  New  York  in 
1898  for  $26  per  ton  containing  90  per  cent  bitumen.  And  it 
should  be  remembered  that  in  purchasing  any  asphalt  the  amount 
of  contained  bitumen  should  always  be  stated,  as  this  ingredient 
represents  the  valuable  portion  of  the  material. 

The  market  price  of  refined  Trinidad  asphalt  in  the  New  York 
market  is  about  $30  per  ton. 


ASPHALT  PAVEMENTS.  251 

The  following  are  the  lowest  bids  for  asphalt  received  at  the 
times  and  places  enumerated  in  1900: 

Borough  of  Manhattan,  N.  Y.,  May  10 $2.04 

Borough  of  Brooklyn,  N.  Y.,  May  10 2.35 

Akron,  O.,  May  7 1.96 

Erie,  Pa.,  April  26 2.19 

Louisville,  Ky.,  April  27 1.39 

Norfolk,  Va.,  April  25 2.24 

Detroit,  Mich.,  April  23 2.05 

Newark,  N.  J.,  April  12 2.06 

Chicago,  111.,  April  11 1.95 

Omaha,  Neb.,  March  10 1.90 

Cohoes,  N.  Y.,  May  9 2.66 

Hartford,  Conn 2.46 

Glens  Falls,  N.  Y 2.13 

Joliet,   111 1.70 

(  Wearing  surface 0.94 

Seattle,  Wash.  J 

|  Binder   0.47 

The  above  prices  are  supposed  to  be  for  a  five-year  guarantee 
and  to  include  the  base,  except  in  New  York  City,  where  the  guar- 
antee is  for  ten  years  and  the  price  is  for  wearing  surface  and  binder 
only.  In  Newark  and  Omaha  an  additional  price  of  25  cents  was 
bid  for  ten  years'  guarantee. 

Asphalt  for  Bridges. 

Asphalt  pavement  has  been  laid  on  several  bridges.  Perhaps 
the  most  notable  case  of  this  kind  is  the  Fourteenth  Street  viaduct 
in  Denver,  Col.  One  section  of  this  structure  is  of  steel  for  a 
length  of  about  1500  feet,  having  a  grade  of  4.25  per  cent  for  a 
distance  of  400  feet.  The  entire  roadway  is  paved  with  asphalt  on 
a  concrete  base. 

Expansion- joints  are  provided  at  every  other  post,  making  them 
from  40  to  60  feet  apart,  according  to  the  length  of  the*  bents.  At 
these  joints  three-inch  openings  were  left  in  the  concrete  extend- 
ing across  the  roadway. 

When  the  asphalt  was  laid  these  openings  were  filled  with  pav- 
ing mixture  and  tamped  flush  with  the  top  of  the  concrete,  and  the 
wearing  surface  laid  over  the  whole.  While  still  hot  a  cut  was  made 
on  the  line  AB,  Fig.  16,  and  then  filled  with  hydraulic  cement,  in 
order  to  prevent  the  edges  from  adhering  under  the  action  of  the 


252        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

roller,  and  to  allow  the  contraction  to  occur  at  one  place  should 
there  be  any  appreciable  amount. 

While  this  pavement  was  only  laid  in  September,  1899,  in  May, 
1900,  it  was  in  good  condition,  including  the  joints,  although  it 

A 


SLOTTED   HOLE 


FIG.  16. 

Lad  been  subjected  to  a  temperature  of  20°  below  zero  the  preceding 
winter. 

American  Asphalt  in  Europe. 

In  1885  a  pavement  was  laid  in  Paris  with  Trinidad  asphalt, 
but  was  not  successful,  owing,  it  was  supposed,  to  heavy  traffic. 

A  specimen  pavement  was  laid  some  years  afterwards  in  Lon- 
don, of  which  the  vestry  of  St.  Margaret  and  St.  John  the  Evangel- 
ist, Westminster,  say  in  their  report  for  the  year  ending  Lady-day, 
1899: 

"  After  an  experiment  had  been  made  with  Trinidad  asphalte 
in  James  Street,  the  specifications  for  asphalte  tenders  were  re- 
vised so  as  to  embrace  other  varieties  of  asphalte  paving  hitherto 
excluded.  It  yet  remains  to  be  seen  how  far  this  class  of  asphalte 
is  suitable  for  heavy  traffic." 

As  a  result  of  the  above  action  bids  were  accepted  April  26, 
1899,  for  paving  portions  of  six  different  streets  with  Trinidad 
-asphalt. 

In  1898  a  portion  of  one  street  in  Glasgow  was  paved  with 
Alcatraz  asphalt.  The  first  two  mixtures  were  unsatisfactory,  but 

i 


ASPHALT  PAVEMENTS.  253 

the  third  trial  resulted  in  a  pavement  that  after  fourteen  months' 
heavy  traffic  was  in  perfect  condition. 

Asphaltina. 

A  pavement  somewhat  similar  to  asphalt  has  been  laid  in  sev- 
eral Eastern  States  during  the  past  few  years,  with  a  preparation  of 
coal-tar  as  the  cementing  material. 

The  following  condensed  description  is  taken  from  the  patent 
specifications: 

Coal,  wood,  or  petroleum  tar  is  heated  to  a  temperature  of  from 
280°  to  350°  F.  to  expel  the  water  and  the  more  volatile  hydro- 
carbon ingredients.  To  temper  this  material  and  render  it  tough, 
sulphur  is  added  at  this  temperature,  and  mixed  with  the  tar  gradu- 
ally or  in  small  quantities,  waiting  after  each  addition  of  sulphur 
for  the  chemical  action  to  subside.  The  exact  proportion  of 
sulphur  depends  upon  the  degree  of  hardness  and  tenacity  which  is 
required  in  the  final  product,  but  is  approximately  from  10  to  20 
parts  by  weight  to  from  175  to  300  parts  of  tar. 

The  chemical  action  of  the  sulphur  takes  place  approximately 
at  a  temperature  of  310°  F.,  differing  somewhat  according  to  the 
nature  of  the  tar,  and  consists  partly  in  the  elimination  of  the 
more  volatile  hydrocarbon,  as  sulphuretted  hydrocarbon  compound, 
which  are  not  volatile,  except  at  temperatures  above  400°,  and 
which  remain  and  play  an  important  part  in  the  uniformity  and 
stability  of  the  product.  When  all  the  sulphur  has  been  added  the 
temperature  is  raised  to  about  400°  to  drive  off  the  gases  or  vapors. 
The  temperature  of  the  sulphurized  tar  is  next  lowered  to  about 
280°  F.,  and  an  equal  quantity,  or  thereabouts,  of  rosin  is  added, 
and  thoroughly  mixed  with  the  sulphurized  tar.  The  temperature 
of  the  mixture  is  kept  at  from  280°  to  350°  F.  until  a  perfect  union 
of  the  ingredients  has  taken  place. 

A  paving-cement  is  formed  from  this  primary  composition  by 
mixing  with  it  a  sulphurized  heavy  hydrocarbon  whose  boiling- 
point  after  evaporation  of  the  water  contained  in  it  is  400°  F.  or 
higher. 

Petroleum  residuum  is  generally  used  for  this  purpose,  treated 
by  heating  it  to  a  temperature  of  about  350°  F.  and  adding  sulphur 


254        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

thereto,  about  1  part  by  weight  of  sulphur  to  8  parts  of  residuum. 
The  sulphur  drives  off  the  lighter  hydrocarbon,  and  enables  the 
heavy  hydrocarbon  to  better  resist  changes  in  temperature  and 
other  influences.  This  sulphurized  heavy  hydrocarbon  is  intimately- 
mixed  with  the  primary  composition  at  a  temperature  of  from  280° 
to  350°  F.,  and  may  be  added  to  the  primary  composition,  in  the 
vessel  in  which  the  latter  is  prepared,  as  soon  as  the  ingredients  of 
the  primary  composition  have  become  thoroughly  united.  The 
mixture  is  then  ready  for  use. 

The  following  are  extracts  from  specifications  for  mixing  the- 
wearing  surface  of  asphaltina: 

"  The  wearing  surface  shall  be  composed  of  refined  asphaltina;. 
a  sulphurized  hydrocarbon  flux,  or  softening  element;  fine,  clean,, 
sharp  sand;  and  argilliferous  earth  finely  powdered. 

"  The  asphaltina  used  shall  be  thoroughly  refined,  and,  as  far 
as  possible,  freed  from  organic  and  animal  matter  and  volatile  oil,, 
and  must  contain  at  least  75  per  cent  of  bitumen  soluble  in  bi- 
sulphide of  carbon. 

"  Sulphurized  Hydrocarbon  Flux. — The  sulphurized  hydrocar- 
bon flux,  or  softening  element,  shall  be  made  from  residuum  oil 
obtained  by  distillation  of  petroleum,  which  must  be  free  from 
water,  coke,  light  oil,  and  other  objectionable  impurities,  and  of 
specific  gravity  18  to  20  Beaume  before  being  sulphurized,  and 
must  bear  without  vaporizing  a  fire-test  of  350°  F. 

"  Sand. — The  sand  used  shall  be  fine,  clean,  and  sharp,  and 
upon  being  shaken  with  water  must  not  show  more  than  3  per  cent 
by  volume  of  loam.  It  shall  be  of  such  size  that  none  shall  pass. 
an  80-mesh  sieve,  and  the  whole  shall  pass  a  No.  20  screen. 

"Argilliferous  Earth. — The  powdered  argilliferous  earth  shall 
be  of  such  fineness  that  at  least  16  per  cent  by  weight  shall  be 
an  impalpable  powder,  and  the  whole  of  it  shall  pass  a  No.  40 
screen. 

"  Asphaltina  Cement. — The  asphaltina  cement  shall  consist  of 
refined  asphaltina  in  combination  with  the  sulphurized  hydro- 
carbon flux,  or  softening  element.  The  proportions  of  the  sul- 
phurized hydrocarbon  flux,  or  softening  element,  may  be  varied 
from  time  to  time,  as  directed  by  the  Commissioner,  between  10 
and  15  per  cent,  but  these  percentages  may  be  varied  according  to 


ASPHALT  PAVEMENTS.  255 

circumstances,  as  may  be  necessary  to  secure  the  best  practical  re- 
sults. 

"Pavement  Mixture. — The  asphaltina  cement  shall  be  mixed 
with  sand  and  powdered  argilliferous  earth.  The  proportion  of 
asphaltina  cement  to  a  given  quantity  of  sand  may  vary  from  14  to 
16  of  the  surface  mixture,  according  to  the  quality  and  character 
of  the  sand.  The  powdered  argilliferous  earth  may  be  reduced  or 
omitted  entirely  when  suitable  sand  can  be  obtained.  The  per- 
centage of  bitumen  (soluble  in  bisulphide  of  carbon)  in  any  sur- 
face mixture  shall  not  be  less  than  9  per  cent.  It  is  supposed  to 
produce  a  wearing  surface  in  which  the  voids  between  the  particles 
of  any  one  size  shall  be  filled  as  nearly  as  possible  by  the  next 
smaller  particles,  and  the  final  void  between  the  smallest  particles 
filled  with  as  thin  a  layer  as  possible  of  asphaltina  cement." 

The  actual  mixing  of  the  different  ingredients,  as  well  as  the 
laying  of  the  pavement,  is  practically  the  same  as  that  of  the  ordi- 
nary sheet  asphalt. 

It  costs  on  a  concrete  base  about  $2.50  per  square  yard. 

Asphalt  Block  Pavement. 

Another  form  of  asphalt  pavement  is  that  known  as  asphalt 
block.  Blocks  of  crushed  stone  and  Trinidad  asphalt  were  first 
made  in  San  Francisco  in  1869.  The  machinery,  however,  was  very 
crude,  hand-moulds  being  used,  and  the  compressing  was  done  by 
men.  The  results,  as  might  have  been  expected,  were  poor,  but 
the  success  of  the  blocks  was  such  that  their  manufacture  was  con- 
tinued to  a  greater  or  less  extent  for  ten  years  when,  about  1880, 
the  invention  of  a  powerful  mechanical  press  made  the  manufacture 
of  improved  blocks  possible  and  successful.  From  that  time  on, 
improvements  have  been  made  upon  the  methods  and  machinery. 

For  quite  a  number  of  years  the  blocks  were  made  of  limestone, 
but  in  1893  trap-rock  was  substituted  for  the  limestone.  Blocks 
made  of  this  latter  material  give  much  better  satisfaction  on  ac- 
count of  the  greater  durability  of  the  trap-rock,  and  at  the  present 
time  that  material  is  being  used  entirely  in  the  manufacture  of  the 
blocks.  Asphaltic  cement  is  mixed  with  the  trap-rock  in  proper 
proportions  at  a  temperature  of  about  300°.  The  material  is  placed 


256        STREET  PAVEMENTS  AND  PAYING  MATERIALS. 

in  a  press  at  this  temperature  and  each  block  is  subjected  to  a 
pressure  of  120  tons.  After  leaving  the  press  the  blocks  are  gradu- 
ally cooled  in  a  water-bath,  and  are  then  ready  for  use. 

In  the  earlier  years  of  the  industry  blocks  were  made  4  x  5  x  12 
inches.  A  depth  of  5  inches,  however,  was  considered  to  be  un- 
necessary, and  the  present  practice  makes  them  of  the  same  dimen- 
sions as  above,  except  that  the  depth  is  4  and  3  inches,  the  blockb 
weighing  13J  and  18  Ibs.  respectively.  These  blocks  are  carried 
to  the  street  and  laid  upon  a  base  of  either  gravel,  broken  stone, 
or  concrete,  as  the  case  may  be. 

The  blocks  are  laid  in  practically  the  same  manner  as  are  bricks, 
the  joints  being  filled  with  fine  sand.  The  advocates  of  this  sys- 
tem claim  the  advantage  of  uniformity  in  manufacture;  that  the 
materials  are  always  mixed  in  exactly  the  same  proportions  and  at 
the  same  temperatures;  that  the  blocks  are  made  under  cover  and 
are  not  subject  to  any  differences  on  account  of  changes  in  the 
weather;  also  that,  as  the  blocks  are  manufactured  at  one  central 
plant,  they  can  be  used  in  cities  of  small  size  without  the  expense 
of  the  location  of  portable  plants.  These  arguments  are  good,  but, 
as  all  the  material  must  be  first  transported  to  the  plant  and  then 
the  blocks  carried  to  the  place  where  they  are  to  be  used,  the  cost 
of  this  double  transportation  in  some  localities  prevents  them 
from  competing  successfully  from  an  economical  standpoint  with 
the  sheet  asphalt.  Wherever  used,  asphalt  blocks  have  given 
satisfaction.  It  is  claimed  that  they  can  be  laid  successfully  on 
much  steeper  grades  than  sheet  asphalt,  and  that,  on  account  of 
their  being  so  very  solid  and  compact,  they  do  not  require  as  thick 
a  concrete  base  as  the  sheet  asphalt.  On  January  1,  1900,  there  had 
been  laid  in  this  country  1,655,532  yards  of  this  class  of  pavement. 
Quite  an  amount  also  has  been  laid  in  South  America,  and  some  in 
Europe. 

The  cost  of  asphalt-block  pavement  varies  with  location  of  city, 
depth  of  blocks,  character  of  foundation,  etc.  . 

For  4-inch  blocks  laid  on  natural-cement  concrete  4  inches 
thick  the  price  will  range  from  $2.40  to  $2.70  per  square  yard,  and 
for  3-inch  blocks  about  25  cents  less. 

Another  form  of  asphalt  blocks  is  sometimes  used  in  which  the 
broken  stone  is  replaced  by  granulated  cork.  Such  blocks  were  laid 


ASPHALT  PAVEMENTS.  257 

on  Fifth  Avenue,  New  York,  between  Thirty-fourth  and  Thirty- 
sixth  streets,  in  strips  ten  feet  wide,  adjacent  to  the  curb.  The 
grade  on  these  two  blocks  being  somewhat  steeper  than  the  re- 
mainder of  the  avenue,  it  was  deemed  best  to  provide  a  better  foot- 
hold for  horses  in  slippery  weather  than  the  ordinary  asphalt.  The 
blocks  are  2  x  4J  x  9  inches  and  were  set  flatwise.  This  pavement 
was  laid  in  the  fall  of  1897,  and  in  the  spring  of  1900  was  in  very 
good  condition.  It  cost  $5.25  per  square  yard,  exclusive  of  founda- 
tion, under  a  fifteen  year  guarantee. 

Although  very  desirable  for  driveways  and  bridges,  cork  blocks 
can  never  be  very  generally  used  on  account  of  their  excessive 
cost. 


CHAPTEE  IX. 

BRICK   PAVEMENTS. 

BRICK  pavements  have  been  used  in  Holland  since  the  thir- 
teenth century.  In  the  seventeenth  century  the  roads  from  the 
Hague  to  the  Scheveningen  were  paved  with  brick.  These  brick 
were  7f  inches  long,  2  inches  wide,  and  4  inches  deep.  Holland,, 
having  no  natural  material  of  its  own  suitable  for  pavements,  was. 
fortunate  in  being  able  to  make  bricks  out  of  the  silt  and  deposits 
of  the  river,  which  have  been  very  successful  in  pavements.  Some 
stone  has  been  used  in  the  larger  cities,  most  of  it  having  been 
brought  from  Sweden.  Amsterdam  and  Rotterdam  at  the  present 
time  use  brick  quite  extensively,  the  former  city  having  now  about 
181,500  square  yards.  The  life  of  the  brick  pavement  there  is  said 
to  be  on  an  average  of  from  ten  to  twenty  years.  In  Amsterdam 
it  is  generally  used  on  one  side  for  ten  years,  when  the  bricks  are 
turned,  after  which  they  will  last  about  four  years,  making  a  total 
life  of  fourteen  years.  The  foundation  is  usually  a  bed  of  sand  from 
8  to  12  inches  deep. 

It  is  said  that  Japan  has  had  brick  pavements  for  more  than 
one  hundred  years,  and  one  authority  gives  the  dimensions  of  the 
brick  as  7  inches  long,  4  inches  deep,  and  1 J  inches  thick.  Inquiry 
made  of  the  authorities  in  Yokohama  elicited  the  following  reply: 

"  I  have  to  say  that  the  brick  pavements  in  use  in  Osaka  since 
very  ancient  times  are  composed  of  broken  roofing-tiles  set  on  end, 
usually  obtained  from  debris  of  houses  after  conflagration.  Heavy 
traffic  quickly  destroys  these  pavements." 

England  has  never  used  brick  to  any  great  extent  in  pavements; 
but  in  Staffordshire  so-called  blue  brick,  described  in  detail  in  a 
previous  chapter,  are  said  to  have  been  in  use  for  about  fifty  years. 

In  the  United  States  the  first  brick  pavement  was  laid  in 

258 


BRICK  PAVEMENTS.  259 

Charleston,  W.  Va.,  in  1870.  This  was  a  small  portion  of  the  prin- 
cipal street  in  the  city,  laid  by  a  private  citizen  at  his  own  expense, 
without  any  encouragement  from  the  city  and  despite  the  ridicule 
of  the  spectators.  The  city  paid  no  portion  of  the  expense.  The 
pavement  was  so  good,  however,  that  in  1873  the  experiment  was 
continued  on  a  larger  scale,  the  city  paying  the  cost.  This  latter 
pavement,  although  laid  twenty-seven  years  ago,  is  said  to  be  still 
good  and  to  have  received  very  little  repairs.  This  brick  was  a 
hard-burned  building-brick,  and  samples  taken  up  after  having 
been  down  twenty  years  showed  a  wear  of  J  to  £  inch.  Its  specific 
gravity  was  2.48. 

In  Bloomington,  111.,  in  1875  half  a  block  of  brick  pavement 
was  laid.  The  brick  were  of  local  manufacture.  So  successful  was 
this  experiment  that  in  1877  the  city  made  a  contract  for  paving 
half  a  block  of  Centre  Street.  This  street  was  relaid  in  1894,  and 
Avhen  taken  up  the  brick  were  found  to  be  worn  about  three- 
quarters  of  an  inch.  This  pavement  consisted  of  two  courses  of 
brick,  the  bottom  course  being  laid  flat  and  the  top  course  on  edge 
upon  it. 

Wheeling,  W.  Va.,  adopted  brick  for  paving  purposes  in  1883. 
These  brick  were  laid  on  tarred  boards  on  a  sand  base,  with  a 
cushion  of  about  1  inch  of  sand  between  the  boards  and  the  brick. 
Brick  in  Wheeling  have  entirely  superseded  cobblestone,  which 
was  the  only  paving  material  previous  to  1883.  About  18  miles 
have  now  been  laid. 

Steubenville,  Ohio,  laid  its  first  brick  pavement  in  1884.  A 
letter  from  the  official  in  charge  of  streets  in  1899  says:  "The 
pavement  is  still  in  good  condition,  has  required  no  repairs,  and 
from  present  indications  will  last  ten  years  longer  without  repairs. 
These  brick  were  laid  on  a  foundation  of  2  inches  of  sand  and  6 
inches  of  gravel,  the  joints  being  filled  with  sand." 

Galesburg,  111.,  where,  at  the  present  time,  so  many  first-class 
paving-brick  are  being  manufactured,  also  first  began  their  use  in 
1884. 

Brick  pavement  were  first  used  in  Zanesville,  0.,  in  1885.  The 
City  Engineer  in  1899  says:  "  By  reason  of  relaying  the  street-rail- 
way- tracks,  this  pavement  was  torn  up  and  relaid  three  years  ago. 
New  bTicks  were  used,  as  many  were  broken,  and  the  wedge-shaped 


260         STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

bricks  used  in  1885  were  no  longer  obtainable  or  desirable.  A 
small  part  of  this  portion  of  the  street  is  still  in  position  and 
serviceable,  showing  good  wearing  qualities." 

Peoria,  111.,  first  constructed  brick  pavement  in  1885.  This 
consisted  of  two  courses  of  brick,  laid  on  a  gravel  foundation,  with 
a  layer  of  sand  between  the  two  courses.  The  material  was  simply 
hard,  specially  selected  local  building-brick.  In  1899  the  City 
Engineer  said:  "  The  street  at  present  is-  in  very  bad  condition, 
and  should  have  been  repaved  before  now.  No  money  has  been 
spent  for  repairs  except  for  openings  for  service  connections." 

Of  the  larger  cities  of  the  country,  Philadelphia  was  the  first 
to  adopt  brick,  laying  its  first  pavements  of  that  material  in  1887. 
So  popular,  however,  did  it  become  there  that  its  use  continually 
increased,  until  at  the  present  time  it  has  a  greater  mileage  of  brick 
pavement  than  any  other  city  in  the  country,  and  in  fact  in  the 
world. 

*•  New  York  City,  south  of  the  Harlem  Biver,  has  but  one  block 
of  brick  pavement.  This  was  laid  in  1891  on  a  cement-concrete 
base,  the  joints  being  filled  with  paving-cement.  The  work  was 
done  (as  is  usual  under  such  circumstances)  as  an  experiment.  The 
brick  with  which  it  was  laid  were  called  pyrogranite  and  were  made 
in  New  Jersey  under  a  special  patent.  It  was  claimed  by  the 
patentee  that  by  treating  any  clay  with  this  process  a  good  paving- 
brick  could  be  made.  These  brick  were  8^  inches  long,  5J  inches 
deep,  and  2}  inches  thick.  Although  having  been  in  use  nearly 
nine  years,  subjected  to  the  heavy  traffic  of  a  street-car  street, 
with  an  elevated  structure  also  in  the  centre,  the  pavement  is 
now  in  good  condition  and  has  received  almost  no  repairs.  This 
being  a  patented  article,  and  having  been  so  successful,  it  will  be 
interesting  to  compare  an  analysis  of  this  brick  with  that  of  the 
Metropolitan  block  of  Canton,  0.,  which  is  conceded  to  be  one  of 
the  very  best  paving-bricks. 

TABLE  No.  65. 

Sesquis-  Absorption 

Silica.      Alumina.       oxide       Lime.    Magnesia.  End-section 
of  Iron.  in  24  Hours. 

Pyro-granite  73.03         22.46        2.94        0.25        trace       0.47 

Metropolitan  block..   63.74        22.86        8.81         0.65         1.82         1.82 


BRICK  PAVEMENTS.  261 

The  success  of  these  early  brick  pavements  is  somewhat  sur- 
prising. It  is  especially  so  when  the  quality  of  the  brick  used  at 
that  time  is  considered,  as  well  as  the  method  of  laying.  The 
brick-manufacturers  then  had  very  little  idea  of  the  possibilities, 
of  a  vitrified  brick.  With  too  many  people  a  brick  simply  meant  a 
brick.  Then  also,  with  the  best  intentions,  no  one  was  able  to 
select  the  best  material.  The  best  of  the  brick  used  at  that  time 
would  not  be  considered  as  a  paving  material,  even/ at  present 
It  is  not  strange,  either,  that  brick  were  not  taken  up  more 
rapidly  as  a  paving  material.  Engineers  as  a  class  are  proverbially 
conservative.  They  never  do  anything  without  a  precedent  unless 
obliged  to.  It  was  hard  for  them  to  believe  that  any  artificial  prod- 
uct could  equal  even  the  productions  of  nature,  but  some  people 
did  have  faith  in  burned  clay,  and  by  their  persistent  efforts  have 
succeeded  in  establishing  brick  in  the  front  ranks  of  paving  ma- 
terials. In  fact,  a  great  many  actually  believe  that  it  is  the  best 
material  for  street  pavements  under  almost  all  conditions,  and  the 
most  radical  advocates  offer  to  guarantee  a  brick  pavement  to  with- 
stand the  traffic  equally  as  well  as  granite.  That  it  is  bound  to  be 
the  principal  paving  material  in  the  Central  West,  where  natural 
stone  can  only  be  obtained  at  a  great  expense,  and  where  clays  and 
shales  are  especially  adapted  for  brick-making,  is  sure. 

To  make  a  good  pavement  bricks  should  be  hard,  tough,  strong,, 
homogeneous,  impervious  to  water,  and  dense. 

Hardness. 

A  paving-brick  must  be  hard  in  order  to  withstand  the  action 
of  the  traffic  and  impact  of  the  horses'  shoes.  It  is  the  one  thing^ 
which  is  naturally  looked  for  by  the  inspectors  on  the  street,  and 
it  is  sometimes  extremely  difficult  to  draw  the  line  between  a  hard 
and  a  soft  brick,  between  one  that  should  and  one  that  should  not 
be  used.  The  color  can  sometimes  be  taken  as  a  guide,  and  in  fact 
almost  always  if  one  is  acquainted  with  the  particular  make  of 
brick;  but  it  will  be  impossible  to  pass  judgment  upon  one  make 
of  brick  by  any  standard  that  has  been  arrived  at  from  an  exami- 
nation of  brick  made  from  entirely  different  clay.  In  fact,  when 
a  new  brick  is  presented  for  use,  a  careful  study  must  be  made  of 
its  characteristics,  so  that  one  may  be  able  to  detect  the  difference 


262        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

by  its  general  appearance.  After  having  determined  this,  the 
color  is  a  pretty  sure  indication  of  the  hardness  of  the  brick. 
Engineers,  as  a  rule,  have  not  made  any  attempt  to  measure  the 
hardness  of  the  brick,  and  very  few  specifications  say  anything 
definitely  upon  this  subject.  Brick,  however,  can  be  easily  tested 
for  hardness  by  the  use  of  Mohs'  scale. 

The  scale  of  hardness  as  introduced  by  Mohs  consists  of  the 
following  minerals: 

1.  Talc:   Common,  laminated  light  green  variety. 

2.  Gypsum:   Crystalline  variety. 

3.  Calcite:   Transparent  variety. 

4.  Fluorite:   Crystalline  variety. 

5.  Apatite:   Transparent  variety. 

6.  Orthoclase:   White  cleavable  variety. 

7.  Quartz:  Transparent. 

8.  Topaz:   Transparent. 

9.  Corundum:  Cleavable  varieties. 
10.  Diamond. 

The  hardness  of  a  substance  may  be  found  by  attempting  to 
scratch  it  with  any  of  the  above  minerals.  For  instance,  if  a  brick 
will  scratch  apat'ite  but  not  orthoclase,  its  hardness  must  be  be- 
tween 5  and  6.  If  it  scratches  quartz  and  is  also  scratched  by  it 
in  about  the  same  degree,  it  is  of  about  the  same  hardness  and  is 
consequently  7.  To  determine  the  percentage  between  the  above 
will  require  considerable  practice,  as  it  depends  upon  the  readiness 
with  which  one  mineral  scratches  the  other. 

A  rough  test  for  hardness  of  a  paving-brick  can  be  made  by 
attempting  to  scratch  glass.  If  it  slightly  scratches  it,  the  hard- 
ness can  be  taken  as  about  5,  and  if  it  scratches  it  readily,  its  hard- 
ness will  be  practically  6. 

Toughness. 

A  very  hard  brick  is  apt  to  be  brittle,  and  unless  it  is  tough  it 
will  crumble  under  traffic  and  be  of  little  use  in  a  pavement.  This 
probably  is  the  most  important  quality  that  the  brick  possesses,  as 
almost  any  paving-brick  is  sufficiently  hard  to  withstand  the  weight 
of  the  traffic,  but  may  not  be  able  to  endure  the  blows  of  the 
wheels  or  of  the  horses'  feet. 


BRICK  PAVEMENTS.  263 

When  an  engineer  is  unable  to  make  a  thorough  test  of  any 
brick  submitted  for  examination,  if  the  test  for  toughness  can  be 
applied  and  it  is  satisfactory,  he  would  be  comparatively  safe  in 
adopting  it  for  use. 

Strength. 

A  brick  should  be  strong,  because,  on  however  good  a  founda- 
tion it  may  be  laid,  or  however  well  bedded,  it  is  liable  to  be 
loaded  at  times  unequally,  and  if  not  possessed  of  sufficient  strength 
is  likely  to  fracture.  As  vitrified  brick  are  made  to-day,  however, 
there  is  very  little  danger  on  these  points,  and  it  is  very  seldom  that 
the  brick  that  will  pass  the  test  for  hardness  or  toughness  will  be 
rejected  on  account  of  its  lack  of  strength. 

• 

Homogeneity. 

Unless  the  particles  of  the  brick  are  perfectly  fused  and  have 
become  one  complete  new  mass,  it  cannot  have  obtained  its  full 
strength.  If  it  be  subjected  to  any  sudden  strain,  it  is  liable  tp 
fracture  between  the  particles  of  which  it  is  made,  when,  if  thor- 
oughly burned  and  vitrified,  the  fracture  should  be  regular  with- 
out any  regard  to  its  previous  make-up.  It  should  be  free  from 
all  marks  of  the  machine  with  which  it  is  mixed,  as  they  both 
weaken  the  brick  physically  and  allow  spaces  for  moisture  to  col- 
lect. 

Uniformity. 

All  products  of  the  same  kiln  should  be  uniformly  burned. 
While  this  is  sometimes  difficult  to  be  obtained,  if  proper  care  is 
exercised  in  the  burning,  and  the  brick  are  selected  at  the  kiln  be- 
fore shipment,  satisfactory  results  can  be  secured  in  almost  every 
instance.  A  better  pavement  will  result  from  a  lot  of  brick  that  are 
uniformly  burned,  even  if  not  up  fully  to  the  required  standard, 
than  from  a  lot  which  is  perhaps  one  half  perfect  and  the  other 
half  somewhat  inferior,  for  when  subjected  to  traffic  the  harder 
brick  will  maintain  their  size,  while  the  softer  brick  will  wear  and 
the  entire  surface  soon  become  rough  and  uneven  and  very  dis- 
agreeable for  travel. 


264:        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


Imperviousness  to  Moisture. 

The  porosity  of  a  paving-brick  is  one  that  can  be  easily  tested 
and  has  received  considerable  attention  by  engineers.  It  has  been 
generally  considered  that  2  per  cent  is  the  maximum  amount  of 
absorption  that  a  good  paving-brick  should  be  allowed.  Very  few 
good  shale  bricks  will  exceed  this,  but  bricks  manufactured  from 
fire-clays,  which  from  their  nature  are  incapable  of  vitrification,, 
will  in  almost  every  case  absorb  more  than  this  amount.  It  has. 
generally  been  considered  that  the  danger  of  absorption  in  a  pav- 
ing-brick was  similar  to  that  in  building-bricks,  that  is,  its  liability 
to  disintegrate  under  the  action  of  frost,  but  it  must  be  remem- 
bered that  paving-brick  and  building-brick  are  two  different  sub- 
stances. In  order  to  reach  the  point  of  vitrification  brick  have 
been  subjected  to  so  severe  a  heat  that  they  have  acquired  a 
strength  which  is  fully  able  to  withstand  all  actions  of  the  frost,, 
and  tests  made  have  borne  out  this  view  of  the  question.  Tests 
for  porosity,  however,  are  valuable,  as  they  indicate,  in  a  way  not 
otherwise  possible,  the  amount  of  vitrification  that  has  taken, 
place,  especially  on  the  exterior.  If  the  brick  be  thoroughly  vitri- 
fied, it  cannot  be  porous  and  cannot  absorb  any  appreciable  amount 
of  water.  While  this  test  should  not  be  given  up  entirely,  it  does- 
not  at  the  present  time  receive  as  much  attention  from  engineers. 
as  it  formerly  did. 

Density. 

Density  is  measured  by  specific  gravity,  and  specific  gravity  is 
measured  by  the  amount  of  material  contained  in  any  substance. 
If,  then,  one  brick  be  of  greater  specific  gravity  than  another,  it 
must  contain  more  wearing  material  and,  other  things  being -equal, 
will  endure  longer  under  traffic.  The  specific  gravity  can  of  course 
be  easily  obtained  in  a  laboratory  by  the  usual  process. 

While  it  is  comparatively  easy  to  specify  the  qualities  that  a 
paving-brick  should  have,  it  is  not  always  so  simple  to  decide  in 
what  way  its  different  properties  should  be  ascertained  when  any- 
particular  brick  axe  presented  for  examination.  When  specifica- 
tions are  made  for  paving-brick,  it  is  necessary  to  set  some  standard 


BRICK  PA  YEMENIS.  265 

with  which  to  compare  all  samples  that  are  submitted,  and  also 
to  have  a  positive  and,  if  possible,  simple,  method  of  determining 
to  what  extent  the  samples  agree  with  this  standard.  Otherwise 
there  will  be  endless  arguments  with  agents  of  the  different  ma- 
terials, each  one  claiming  every  merit  for  his  product  and  being 
very  prolific  in  reasons  why  it  should  be  adopted.  The  qualities 
which  have  generally  been  considered  to  be  of  most  importance  and 
for  which  standards  of  tests  have  been  adopted  are  toughness, 
crushing  and  tensile  strength,  and  imperviousness  to  moisture. 

In  searching  for  some  method  of  ascertaining  the  amount  of 
wear  that  a  brick  would  sustain  under  traffic  on  the  street,  engineers 
have  made  many  experiments.  An  experiment  which  was  made 
several  years  ago  in  St.  Louis,  detailed  in  the  chapter  on  Pave- 
ments, would  be  satisfactory  and  conclusive  as  far  as  abrasion  of 
the  wheels  is  concerned,  but  it  does  away  entirely  with  the  action  of 
the  horses'  feet.  After  considerable  investigation  it  was  decided  to 
test  the  brick  for  its  qualities  in  an  ordinary  iron-foundry  rattler 
which  is  used  for  polishing  castings.  Bricks  were  placed  in  this 
rattler  together  with  a  quantity  of  iron  scrap  and  revolved  for  a 
certain  length  of  time  and  the  percentage  of  loss  to  the  brick  cal- 
culated. This,  however,  was  soon  found  to  be  a  crude  method,  and 
that  the  results  obtained  in  one  foundry  would  vary  very  much 
from  those  obtained  in  another  when  the  same  kind  of  brick  were 
used.  This  arose  from  the  fact  that  the  rattlers  were  of  different 
sizes,  and  also  because  the  charge  of  brick  and  iron  scrap  varied 
in  each  case.  It  was  soon  seen  that  something  definite  must  be 
adopted  for  this  test  in  order  that  the  results  would  be  of  any  par- 
ticular value,  or  that  tests  made  in  different  sections  of  the  country 
could  be  compared  intelligently.  The  National  Brick  Manufac- 
turers5 Association  were  the  first  ones  to  take  this  up  systematically, 
and  in  1895  a  commission  was  appointed,  composed  of  engineers, 
manufacturers,  and  scientific  men  interested  in  the  subject,  to  re- 
port to  the  Association  a  form  of  test  for  brick.  The  commission 
organized  and  selected  different  members  for  the  investigation  of 
the  different  branches  of  the  subject,  and  reported  to  the  Associa- 
tion in  1897. 


266        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 


Abrasion  Test. 

This  was  under  the  direction  of  Prof.  Edward  Orton,  Jr.,  who, 
after  making  an  exhaustive  set  of  experiments  with  the  rattler  to 
determine  the  proper  dimensions,  rate  of  speed,  and  duration  of 
test,  reported  the  results  to  the  convention. 

Mr.  F.  F.  Harrington  of  St.  Louis  also  made  a  series  of  tests 
on  practically  the  same  lines,  the  results  of  which  agreed  very 
closely  with  that  of  Prof.  Orton  and  which  were  presented  to  the 
convention  at  the  same  time. 

Table  No.  66  shows  the  effect  and  degree  of  loss  of  vitrifica- 
tion, and  the  rate  of  loss  by  rattling,  as  determined  by  Mr.  Har- 
rington. 

TABLE  No.  66. 


Description. 

Per  cent  of  Loss. 

10  Min. 

25  Min. 

40  Min. 

60  Min. 

19.57 
11.70 
22.99 

3.64 

2.48 
7.20 

9.20 
6.64 
13.33 

14.53 
9.54 
17.71 

Well-burned  

Average  

3.50 

9.75 

14.10 

17.50 

Considering  the  charge  to  be  placed  in  the  rattler,  Prof.  Orton 
experimented  with  brick  only  in  the  rattler,  with  brick  and  cast- 
iron  blocks,  and  also  with  bricks  and  blocks  of  stone.  From  the 
different  results  obtained  he  decided  that  the  most  satisfactory 
method  was  with  a  charge  composed  of  brick  only.  The  following 
specifications  for  the  standard  method  of  conducting  the  rattling 
test  were  adopted  by  the  convention: 

1.  Dimensions  of  the  Machine. — The  standard  machine  shall  be 
28  inches  in  diameter  and  20  inches  in  length,  measured  inside  the 
rattling-chamber.  Other  machines  may  be  used  varying  in  diameter 
between  26  and  30  inches,  and  in  length  from  18  to  24  inches;  but 
if  this  is  done,  a  record  of  it  must  be  attached  to  the  official  report. 
The  rattler  may  be  cut  up  into  sections  of  suitable  length  by  the 
insertion  of  an  iron  diaphragm  at  the  proper  point. 


BRICK  PAVEMENTS.  267 

2.  Construction  of  the  Machine. — The  barrels  shall  be  supported 
on  trunnions  at  either  end.    In  no  case  shall  the  shaft  pass  through 
a  rattler-chamber.    The  cross-section  of  the  barrel  shall  be  a  regular 
polygon  having  fourteen  sides.    The  heads  and  staves  shall  be  com- 
posed of  gray  cast  iron,,  not  chilled  or  case-hardened.     There  shall 
be  a  space  of  J  of  an  inch  between  the  staves  for  the  escape  of  dust 
and  small  pieces  of  waste.    Other  machines  may  be  used  having  from 
twelve  to  sixteen  staves,  with  openings  from  $  to  f  of  an  inch  be- 
tween the  staves;  but  if  this  is  done,  a  record  of  it  must  be  attached 
to  the  official  report  of  the  test. 

3.  Composition  of  the  Charge. — All  tests  must  be  executed  on 
charges  composed  of  one  kind  of  material  at  a  time.    No  test  shall 
be  considered  final  where  two  or  more  different  bricks  or  materials 
have  been  used  to  compose  the  charge. 

4.  Quantity  of  tht  Charge. — The  quantity  of  the  charge  shall 
be  established  by  its  bulk  and  not  its  weight.     The  bulk  of  the 
standard  charge  shall  be  equal  to  15  per  cent  of  the  cubic  contents 
of  the  rattler-chamber,  and  the  number  of  whole  brick  whose  united 
volume  comes  nearest  to  this  amount  shall  constitute  the  charge. 

5.  Revolutions  of  the  Charge. — The  number  of  revolutions  for  a 
standard  test  shall  be  1800,  and  the  speed  of  rotation  shall  be  30 
per  minute.    The  belt  power  shall  be  sufficient  to  rotate  the  rattler 
at  the  same  speed  whether  charged  or  empty.     Other  speed-rota- 
tions between  24  and  36  revolutions  per  minute  may  be  used;  but 
if  this  is  done,  a  record  of  it  must  be  attached  to  the  official  re- 
port. 

6.  Condition  of  the  Charge. — The  bricks,  composing  the  charge 
shall  be  dry  and  clean,  and  as  nearly  as  may  be  possible  in  the  con- 
dition in  which  they  were  drawn  from  the  kiln. 

7.  Calculation  of  the  Results. — The  loss  shall  be  calculated  in 
the  per  cents  of  the  weight  of  the  dry  brick  composing  the  charge,, 
and  no  result  shall  be  considered  as  official  unless  it  is  the  aver- 
age of  two  distinct  and  complete  tests  made  on  separate  charges  of 
brick. 

Prof.  A.  N.  Talbot  of  the  University  of  Illinois  has  also  made 
some  important  investigations  in  this  line,  and  he  takes  issue  with 
the  conclusion  of  the  Brick  Manufacturers'  Association  in  the 
adoption  of  brick  alone  for  the  rattler-charge.  In  addition  to  the 


268        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

brick  themselves  he  adds  a  charge  of  standard  foundry  shot,  consist- 
ing of  cast-iron  blocks  of  two  sizes,  the  larger  being  2J  x  3^  x  5J 
inches,  with  edges  rounded  to  -J-inch  radius,  weighing  about  8  Ibs. 
each,  and  the  smaller  size  1  x  1  \  x  2J  inches,  with  rounded  edges, 
weighing  about  1  Ib.  From  his  experiments  he  adopted  as  the 
standard  charge  for  a  24  x  36-inch  rattler  150  Ibs.  of  the  8-lb.  shot 
and  150  Ibs.  of  the  1-lb.  shot.  He  concludes  that  by  this  method 
it  makes  no  difference  how  many  bricks,  within  reasonable  limits, 
are  used  in  a  test;  that  from  5  t6  14  bricks  may  be  tested  and  the 
percentage  of  loss  will  remain  nearly  constant.  His  objection  to 
the  test  proposed  by  the  Brick  Manufacturers'  Association  is  that 
it  requires  a  great  many  bricks  for  a  satisfactory  test,  and  .that 
this  means  that  the  results  will  be  materially  affected;  also  that 
the  metliod  will  not  distinguish  sufficiently  between  soft  and  brittle 
brick,  the  idea  being  that  the  brittle  brick  by  impact  would  show 
as  much  less  as  soft  brick  by  abrasion.  He  made  a  series  of  tests 
at  the  University  of  Illinois,  using  his  and  the  manufacturers' 
standard,  with  brick  whose  characteristics  were  well  known,  and 
concluded  from  the  results  that  the  University  of  Illinois  method 
is  better. 

Mr.  Gomer  Jones,  City  Engineer  of  Geneva,  N.  Y.,  has  patented 
a  rattler  for  testing  paving-brick  which  he  thinks  is  superior  to 
those  previously  in  use.  His  idea  was  that  the  ordinary  rattler 
method  gives  the  result  of  impact  upon  the  brick  rather  than  the 
abrasion,  and  his  machine  was  designed  to  correct  this  evil.  A 
paper  read  before  the  National  Brick  Manufacturers'  Association  in 
February,  1899,  described  it  as  follows: 

"  The  machine  is  a  rattler  with  the  usual  driving-gear  and  ac- 
cessories, differing  from  the  ordinary  rattler  only  in  that,  instead 
of  plain  staves,  it  is  provided  with  staves  having  two  longitudinal 
pockets  in  which  the  bricks  are  inserted  and  held  end  to  end.  These 
pockets  are  3  inches  deep,  leaving  about  1  inch  of  the  brick  pro- 
truding. When  all  the  staves  are  in,  the  interior  of  the  rattler 
is  virtually  a  solid  brick  line.  During  rotation  the  touch  of  the 
abrading  material  is  at  right  angles  to  the  length  of  the  brick  and 
confined  to  the  surface  and  edges  which  are  exposed  in  actual  use. 
There  is  sufficient  space  between  the  brick  for  the  escape  of  any 
dust  or  waste,  and  incidentally  to  allow  the  abrading  material  free 


BRICK  PAVEMENTS.  269 

access  to  the  unsupported  edges  of  the  brick  under  test,  reproduc- 
ing the  Conditions  of  position  and  line  of  wear  found  when  the 
brick  are  laid  with  sand  filler  on  the  street.  In  selecting  abrading 
material,  the  first  point  to  be  decided  is  the  amount  of  wear  or 
abrasion  desirable.  My  opinion  is  that  the  abrasion  should  be  of 
such  amount  that  at  the  end  of  the  test  the  weakest  brick  shall  be 
in  a  condition  similar  to  that  in  which  the  brick  worn  out  on  the 
street  are  found. 

"  I  will  not  enter  into  details  of  the  exhaustive  experiments  that 
led  to  the  adoption  of  the  cast-iron  cube  1 l  /2  inches  square,  weigh- 
ing 87/100  of  a  pound,  as  the  unit,  and  150  Ibs.  of  such  cubes  as  the 
charge,  but  will  simply  state  that  when  subjected  to  3000  revolu- 
tions the  bricks  considered  standard  lost  50  per  cent  of  weight, 
and  would  be  condemned  if  found  on  the  street." 

The  rattler  used  by  Mr.  Jones  was  24  inches  in  diameter.  There 
is  no  question  but  that  his  apparatus  subjects  the  brick  more 
nearly  to  conditions  similar  to  what  it  receives  on  the  street 
ihan  that  of  the  ordinary  rattler;  and  as  in  all  tests  the  conditions 
should  be  made  as  nearly  as  possible  like  those  under  which  the 
material  is  subjected  in  the  work,  the  method  is  to  be  commended. 
The  principal  thing,  however,  to  be  obtained  is  to  have  a  test  that 
will  be  standard,  that  will  distinguish  the  different  defects  of  the 
different  kinds  of  brick,  and  by  a  method  that  can  be  repeated  in 
different  cities  with  practically  the  same  results.  This  Mr.  Jones 
expects  to  effect  by  his  machine,  and  it  would  seem  that  his  ex- 
pectations were  justified.  In  a  test  of  certain  kinds  of  brick  and 
cut  Medina  stone  blocks  made  by  him  with  his  machine,  the  losses 
were  as  follows: 

Per  cent. 

Shale  block 2.46 

Medina  stone  block 3.61 

Fire  clay  block  No.  2 3.2 

On  account  of  these  differences  a  committee  was  appointed  by 
the  National  Brick  Manufacturers'  Association  for  further  investi- 
gation, and,  in  consequence  of  its  report  to  the  convention  in  1900, 
sections  3,  4,  and  5  were  modified  to  read  as  follows: 

3.  Composition  of  the  Charge. — All  tests  must  be  executed  on 
charges  containing  but  one  make  of  brick  or  block  at  a  time.  The 


270        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

charge  shall  consist  of  nine  paving-blocks  or  twelve  paving-bricks, 
together  with  three  hundred  pounds  of  shot  made  of  ordinary 
machinery  cast  iron.  This  shot  shall  be  of  two  sizes,  as  described 
below,  and  the  shot  charge  shall  be  composed  of  one-fourth  (75 
pounds)  of  the  larger  size  and  three-fourths  (225  pounds)  of  the 
smaller  size. 

4.  Size  of  the  Shot. — The  larger  size  shall  weigh  about   7£ 
pounds  and  be  about  2J  inches  square  and  4J  inches  long,  with 
slightly  rounded  edges.     The  smaller  size  shall  be  cubes  of  1J 
inches  on  a  side,  with  rounded  edges.     The  individual  shot  shall 
be  replaced  by  new  ones  when  they  have  lost  one-tenth  of  their 
original  weight. 

5.  Revolutions  of  the  Charge. — The  number  of  revolutions  of  a 
standard  test  shall  be  1800,  and  the  speed,  of  rotation  shall  not  fall 
below  28  nor  exceed  30  per  minute.    The  belt-power  shall  be  suf- 
ficient to  rotate  the  rattler  at  the  same  speed  whether  charged  or 
empty. 

It  was  also  recommended  in  the  construction  of  the  rattler  that 
the  staves  be  made  of  steel  on  account  of  the  rapid  wear  of  the  cast 
iron. 

Absorption  Test. 

An  investigation  in  regard  to  this  test  was  also  made  by  Mr. 
Harrington.  He  experimented  in  a  great  many  different  ways,  and 
his  conclusions  were  the  result  of  very  careful  study,  as  is  shown 
in  detail  in  his  report. 

In  order  to  bring  the  samples  to  the  proper  standard  of  dryness, 
they  were  kept  in  an  oven  that  was  constantly  maintained  at  a 
temperature  of  from  220°  to  240°  Fahr. 

Table  No.  67  shows  the  results  of  his  investigations  in  that 
respect,  and  the  following  are  his  conclusions: 

"  This  chart  shows  that  it  requires  four  days  to  dry  the  sam- 
ples of  brick  completely  and  thoroughly,  even  when  the  tempera- 
ture is  maintained  constantly  above  the  boiling-point  of  water. 
This  shows  how  complex  and  tortuous  the  pore-channels  through 
the  mass  of  the  brick  must  be,  since  the  water  exhausted  in  them 
must  be  superheated  and  under  pressure  for  the  entire  time  of  the 
test;  but  while  96  hours  is  necessary  to  complete  the  drying,  still 


BRICK  PAVEMENTS. 


271 


the  amount  of  moisture*  lost  in  the  last  half  of  this  treatment  is 
the  very  small  amount  of  only  5.9  per  cent  of  the  total  quantity 
evaporated.  For  practical  work  the  gain  in  time  of  48  hours  on  a 
test  is  worth  more  than  the  reduction  to  absolute  dryness." 

TABLE  No.  67. 


Brand  of  Brick. 

Percentages  of  Water  Evaporated. 

eJT 

Sb 

KQ 
®* 

•rf 

£* 

Cff 

££ 

g* 

§b 
KQ 
to 

!* 

s 

$t 

^ 

is 

«b 

s° 

Alton  Paving-brick  Co..  Alton,  111  
St  Louis  Pressed-brick  Co.,  St.  Louis,  Mo  

.070 
.065 
.210 
.065 
.075 
.030 
.040 
.035 
.055 
.045 

.085 
.205 
.320 
.095 
.115 
.062 
.195 
.090 
.055 
.060 

-.120 

.232 

.395 
.130 
.168 
.095 
.312 
.120 
.112 
.087 

.185 
.260 
.525 
.130 
.190 
.110 
.330 
.155 
.112 
.120 

.135 
.260 
.535 
.145 
.2^0 
.130 
.355 
.155 
.130 
.120 

.135 
.260 
.535 
.145 
.220 
.130 
.355 
.155 
.130 
.120 

Standard  Paving-brick  Co    St  Louis  Mo           .   . 

Purington  Paving-brick  Co.,  Galesburg,  111  
Barr  Clay  Co    Sti'eator  111  .        .... 

Moberly  Brick  Co    Moberly'  Mo        

Galesburg  Paving-brick  Co.,  Galesburg,  111  
Galesburg  Brick  and  Terracotta  Co.,  Galesburg,  111.  . 

.065 

.127 

.178 

.210 

.220 

.220 

TABLE  No.  68. 

Percentages  of  Water  Absorbed. 


Brand. 

I 

I 

M 

I 

t~ 

2  Weeks. 

4  Weeks. 

6  Weeks. 

8  Weeks. 

12  Weeks. 

24  Weeks. 

Alton  Paving-brick  Co  

0  37 

0  55 

0  65 

0  80 

1  05 

1  29 

1  51 

1  62 

1  73 

St  Louis  Pressed-brick  Co  .... 

0  36 

0.44 

0.44 

0  44 

0.44 

0.44 

0  44 

0.44 

0  45 

Standard  Paving-brick  Co  
Purington  Paving-brick  Co  
Barr  Clay  Co                         .... 

0  44 
0.87 
0  25 

0.55 
1.48 
0  80 

0.60 
1.76 
1  60 

0.70 
1.95 
2  10 

0.76 
2.05 
2  30 

0.87 
2.20 
2  60 

0.96 
2.28 
2  70 

1.02 
2.31 

2  74 

1.12 
2.48 
2  87 

Townseud  Paving-brick  Co  
Moberly  Brick  Co        
Wabasb  ClavCo.,Veedersburg,Ind. 
Mack  Pav.-brick  Co.,  Pittsburg,  Pa. 
Imperial  Pav.  -brick  Co.,Canton,O. 
Des  Moiues  Paving-brick  Co.,  Des 
Moines  la 

0.28 
1.60 
4.60 
3.12 
0.25 

0  60 

0.37 
2.65 
5.30 
3.63 
0.35 

0  75 

0.48 
8.10 
5.63 
3.87 
0.37 

0  76 

0.62 
3.90 
5.87 
4.02 
0.58 

1  03 

0.83 
4.10 
6.10 
4.18 
0.70 

1  25 

0.87 
4.26 
6.20 
4.20 
0.85 

1  45 

1.00 
4.35 
6.35 
4.29 
1.04 

1  62 

1.05 
4.55 
6.40 
4.32 
1.18 

1  73 

1.20 

4.GJ 
6.58 
4.35 
1.28 

1  87 

*  Passing  100-mesh. 


Table  No.  68  shows  the  percentages  of  water  absorbed  at  dif- 
ferent intervals  of  complete  immersion. 

On  another  test  made  with  samples  from  which  both  ends  had 
been  broken,  leaving  practically  half  of  the  brick,  the  result  showed 
a  considerable  gain  over  that  for  which  the  whole  brick  was  used. 


272        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Experiments  were  also  made  with  small  chips  from  the  interior  of 
the  bricks  which  showed  the  same  line  of  facts  as  the  previous  ex- 
periment. He  concludes  that  it  is  doubtful  if  it  would  be  possible  to 
get  complete  saturation  even  if  the  bricks  were  first  put  into  the 
vacuum-chamber  and  the  gas  from  their  pores  exhausted.  The 
average  increase  of  absorption  of  the  half -bricks  over  the  whole  ones 
was  found  to  be  16^  per  cent  in  24  weeks,  and  the  average  increase 
of  small  pieces  over  half -bricks  and  whole  bricks  in  eight  weeks  was 
respectively  47.3  and  66.1  per  cent.  Mr.  Harrington  favors  the 
use  of  the  brick  which  have  first  been  used  in  the  rattler  test, 
because  the  action  of  the  water  by  absorption  takes  place  quicker 
with  such  brick,  and  also  for  the  reason  that  they  are  in  practically 
the  same  condition  as  the  brick  that  are  exposed  in  a  pavement. 
His  reports  having  been  presented  to  the  commission  and  discussed, 
the  following  points  were  agreed  upon  by  all: 

"  1.  That  all  the  evidence  showed  that  all  data  obtained  in  any 
short  test  of  less  than  one  week  is  far  from  representing  the  actual 
porosity  of  the  brick. 

"  2.  That  the  results  of  short  tests  are  misleading,  because  the 
rates  of  absorption  of  different  samples  are  widely  different. 

"  3.  That  in  the  experience  of  members  of  the  commission  no 
connection  whatever  can  be  traced  between  a  low  absorption  test 
and  materials  of  wearing  quality  in  paving-brick. 

"  4.  That  paving-bricks  which  are  soft  enough  to  become  liable 
to  destruction  by  frost  showed  this  structural  weakness  in  the 
rattler  test  also." 

Consequently  the  commission  decided  officially  to  discontinue 
the  absorption  test  as  a  means  of  determining  the  value  of  paving- 
bricks;  but  for  the  benefit  of  those  who  might  still  adhere  to  its 
use,  the  following  specifications  for  conducting  the  test  were 
adopted: 

"  1.  Number  of  Brick. — The  number  of  brick  constituting 
sample  of  the  official  test  shall  be  five. 

"2.  Condition  of  the  Brick. — The  brick  selected  for  conduct- 
ing this  test  shall  be  such  as  have  been  previously  exposed  to  the 
rattler  test.  If  such  are  not  available,  then  each  whole  brick  must 
"be  broken  in  halves  before  the  test  begins. 

"3.  Drying. — The  brick  shall  be  dried  for  48  hours  contin- 


BRICK  PAVEMENTS.  273 

uously  at  a  temperature  of  230°  to  250°  Fahr.  before  the  absorp- 
tion test  begins. 

"  4.  Soaking. — The  brick  shall  be  weighed  before  wet,  and 
sha'l  then  be  completely  immersed  for  48  hours. 

"  o.  Wiping. — After  soaking,  and  before  reweighing,  the 
bricks  must  be  wiped  until  free  from  surplus  water  and  practically 
dry  on  the  surface. 

"  6.  Weighing. — The  samples  must  then  be  reweighed  at  once. 
The  scales  must  be  sensitive  to  1  gram. 

"  7.  Calculation  of  Result. — The  increase  in  weight  due  to 
absorption  shall  be  calculated  in  per  cents  of  the  dry  weight  of 
the  original  bricks." 

The  commission  then  adopted  the  following  resolution  and 
attached  it  to  the  above  as  a  part  of  their  report: 

"  Resolved,  that,  in  the  opinion  of  this  commission,  any  pav- 
ing-brick which  will  satisfy  reasonable  mechanical  tests  will  not 
absorb  sufficient  water  to  prove  injurious  in  service.  We  there- 
fore recommend  that  the  absorption  test  be  abandoned  from  all 
official  tests  as  unnecessary,  if  not  absolutely  misleading." 

/ 

Cross-breaking  Test. 

This  test  is  made  for  the  purpose  of  showing  the  tensile 
strength  of  the  brick.  This  examination  was  also  made  by  Mr. 
Harrington,  and  the  commission  after  considering  his  report 
adopted  the  following  specifications  for  the  standard  method  of 
executing  the  cross-breaking  test  of  paving-brick: 

"  1.  Support  the  brick  on  edge,  or  as  laid  in  a  pavement,  on 
a  hardened  steel  knife  rounded  longitudinally  to  the  radius  of  12 
inches,  and  transversely  to  the  radius  of  £  inch,  and  bolted  in 
position  so  that  the  screw-span  of  6  inches  applied  to  load  in  the 
middle  of  the  top  shall  pass  through  the  steel  knife-edge,  straight, 
longitudinal,  and  rounded  transversely  to  a  radius  of  1/16  inch. 

"  2.  Apply  the  load  to  the  middle  of  the  top  face  through  a 
hardened  steel  knife-edge,  straight,  longitudinally,  and  rounded 
transversely  to  a  radius  of  1/16  inch. 

"  3.  Apply  the  load  in  a  uniform  rate  of  increase  until  frac- 
ture ensues. 


274        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 
"  4.  Complete  the  modulus  of  rupture  by  the  formula 


in  which  F  =  modulus  of  rupture  in  pounds  per  square  inch; 
W  =  the  total  brick  load  in  pounds;  L  =  the  length  of  span  in 
inches,  6;  B  =  breadth  of  brick  in  inches;  D  =  depth  of  brick  in 
inches. 

"  5.  Samples  for  test  must  be  free  from  all  visible  irregularities 
of  surface  or  deformities  in  shape,  and  their  upper  and  lower  faces 
must  be  practically  parallel. 

"  6.  Not  less  than  ten  brick  shall  be  broken,  and  the  average 
of  all  is  to  be  taken  for  the  standard  test." 

The  following  passage  is  quoted  from  one  place  in  Mr.  Har- 
rington's report: 

"  Cross-breaking  test  of  paving-brick  is  made  for  the  following 
reasons: 

"  1.  It  furnishes  the  meajis  of  comparing  the  differences  of 
various  kinds  of  clay  paving  material. 

"  2.  For  any  particular  kind  of  brick  it  shows  whether  the 
brick  has  been  properly  treated  in  the  various  stages  of  its  manu- 
facture. 

"3.  It  indicates  the  resistance  of  the  material  in  cross-break- 
ing when  laid  on  beds  of  unyielding  and  uneven  surface. 

"  4.  The  cross-section  being  exposed,  the  interior  structure 
may  be  examined/' 

In  order  to  obtain,  if  possible,  whether  any  agreement  could 
be  traced  between  excellence  in  cross-breaking  and  excellence  in 
the  other  tests,  the  facts  in  Table  No.  69  were  collected.  The 
bricks  used  were  all  standard  paving-bricks  and  are  given  in  detail 
in  the  report.  From  this  it  will  be  seen  that  excellence  in  one 
test  does  not  at  all  imply  excellence  in  another.  For  instance,  No. 
6,  which  shows  the  least  loss  in  the  rattler  test,  has,  with  one  ex- 
ception, the  largest  amount  of  absorption,  and  has,  with  two 
exceptions,  the  lowest  specific  gravity. 

The  commission,  after  some  discussion,  agreed  to  pass  a  reso- 
lution leaving  the  test  as  permissible  or  optional  with  either 
engineer  or  maker,  without  condemning  it  unqualifiedly  as  had 


BRICK  PAVEMENTS. 


275 


been  done  with  the  absorption  test,  but  at  the  same  time  indicat- 
ing the  opinion  of  the  body  that  the  test  was  not  important  or 
especially  trustworthy. 

Crushing  Test. 

Prof.  J.  B.  Johnson  of  Washington  University  presented  the 
following  specifications  for  the  standard  method  of  making  the 
crushing  test  of  paving-brick: 

TABLE  No.  69. 


Designa- 
tion of 
Sample. 

Clay  Material 
Used. 

Dimensions  of 
Brick. 
Inches. 

Per  cent 
Lost  in 
Rattler 
Test. 

Per  cent 
Gain  in 
Absorp- 
tion Test. 

Specific 
Gravity. 

Modulus 
of  Rup- 
ture in 
Cross- 
breaking. 

1 

Shale 

8     X  3f  X  3 

13.72 

1.52 

2.41 

2669 

2 

8    X  4    X  2i 

14.53 

1.15 

2.34 

3663 

3 

8    X  4    X  2f 

11.45 

1.17 

2.37 

3619 

4 

8f  X  4    X  2£ 

12.94 

1.83 

2.33 

3498 

5 

8|  X  4    X  3* 

10.80 

1.72 

2.35 

3104 

6 

Mixture 

9X4X3 

9.86 

4.09 

2.24 

2842 

7 

Shale 

8    X  3|  X  2i 

18.98 

2.05 

2.33 

2479 

8 

8    X  4    X  2* 

13.34 

0.92 

2.41 

3780 

9 

8    X  4    X  2* 

10.12 

1.05 

2.36 

3618 

10 

8    X  4    X  2i 

12.74 

1.85 

2.28 

2958 

11 

9X4X3 

10.26 

2.48 

2.27 

3056 

12 

Mixture 

9X4X3 

11.95 

2.86 

2.22 

2428 

13 

Fire-clay 

8i  x  4    X  2i 

10.87 

4.78 

2.20 

3221 

DESCRIPTION    OP   TESTS. 

Rattler. — Diameter  of  barrel  24  inches,  length  21  inches.  The  chamber  was 
filled  to  15$  of  its  volume,  and  the  charge  tumbled  40  minutes  at  30  revolutions 
per  minute. 

Absorption. — Five  rattled  bricks  were  dried  48  hours  and  immersed  48  hours. 

Specific  Gravity. — From  some  samples  used  in  the  absorption  test. 

Gross-breaking. — Span  6  inches.    Average  of  10  bricks  broken  on  edge. 

"  1.  The  crushing  test  should  be  made  of  half -brick  loaded 
edgewise,  or  as  they  are  laid  on  the  street.  If  the  machine  used  is 
unable  to  crush  the  full  half-brick,  the  area  may  be  reduced  by 
chipping  off,  keeping  the  form  of  the  piece  to  be  tested  as  nearly 
prismatic  as  possible.  A  machine  of  at  least  10.0,000  Ibs.  capacity 
should  be  used,  and  the  standard  should  not  be  reduced  below  4 
square  inches  area  in  cross-section  at  right  angles  to  direction  of 
load. 

"  2.  The  upper  and  lower  surfaces  should  preferably  be  ground 


276        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

to  true  and  parallel  planes.  If  this  is  not  done,  they  should  be 
bedded  in  plaster  of  Paris  while  in  the  testing-machine,  and  should 
be  allowed  to  harden  ten  minutes  under  weight  of  the  crushing 
plane  only  before  the  load  is  applied. 

"  3.  The  load  should  be  applied  at  a  uniform  rate  of  increase 
to  the  point  of  rupture. 

"  4.  Not  less  than  the  average  obtained  from  five  tests  of  five 
different  bricks  shall  constitute  a  standard  test." 

These  specifications  were  adopted  unanimously. 

After  considerable  discussion  and  consideration  of  data,  the 
commission  adopted  the  following: 

"  Whereas,  from  the  experimental  work  done  so  far  by  this 
commission,  or  by  others,  so  far  as  is  known  to  us  in  the  applica- 
tion of  the  cross-breaking  machine  tests  to  paving-bricks,  it  is 
not  possible  to  show  any  close  relationship  between  the  qualities 
necessary  for  a  good  paving  material  and  high  structural  strength 
as  indicated  by  either  of  these  tests, — 

"  Resolved,  that  for  this  reason  the  commission  recommends 
that  these  tests  shall  be  considered  as  purely  optional  in  the  ex- 
amination of  paving  material,  and  not  necessary  as  a  proof  of  ex- 
cellence." 

Hardness  and  Specific  Gravity. 

Mr.  Harrington  submitted  data  obtained  from  ten  samples  of 
paving-bricks  showing  the  range  of  specific  gravity  from  2.19  up 
to  2.41,  the  majority  being  between  2.25  and  2.35.  The  hardness 
of  a  well-burned  paving-brick  has  been  proven  to  lie  very  close  to 
6  in  Mohs'  scale,  and  it  is  not  possible  by  any  known  process  of 
treatment  to  enable  them  to  reach  the  hardness  of  7.  In  conse- 
quence of  the  small  range  as  measured  in  this  scale,  and  the  im- 
possibility of  suggesting  or  applying  any  other  test  for  hardness, 
the  commission  considered  this  test  of  doubtful  value.  Conse- 
quently the  following  resolution  was  passed: 

"  Whereas,  after  careful  consideration  of  all  the  data  as  to 
hardness  and  specific  gravity  accessible  to  the  commission,  no  re- 
lationship between  these  qualities  and  those  necessary  for  good 
paving-brick  can  be  shown  to  exist, — Therefore, 

"  Resolved,  that  the  commission  recommend  that  this  test  be 
abandoned  as  unnecessary." 


BRICK  PAVEMENTS.  277 

Prof.  Orton  presented  a  paper  to  the  National  Brick  Manu- 
facturers' Association  giving  the  results  of  an  investigation  of  the 
effect  of  structure  on  the  wearing  power  of  paving-brick,  and  in 
a  table  accompanying  it  he  showed  the  average  loss  to  106  end- 
cut  bricks  after  1000  revolutions  of  the  rattler  to  be  19.54  per 
cent,  and  after  2000  revolutions  of  the  rattler  to  be  27  per  cent, 
and  the  average  of  side-cut  bricks  to  be  24.43  per  cent  after 
1000  revolutions,  and  32.9  per  cent  after  2000  revolutions;  that 
of  47  end-cut  plain  bricks  made  on  four  different  machines  in 
nine  different  tests  the  average  loss  was  21.05  per  cent  after  1000 
revolutions,  and  28.48  per  cent  after  2000  revolutions;  and  that 
of  59  end-cut  repressed  bricks  the  loss  was  18.23  per  cent  after 
1000  revolutions,  and  26.67  per  cent  after  2000  revolutions.  The 
average  modulus  of  rupture  for  repressed  bricks  was  2525,  and 
for  end-cut  plain  bricks  2425.  For  side-cut  repressed  brick  the 
average  was  2346. 

After  having  made  all  of  the  above  tests  and  arrived  at  the 
results  of  each  for  any  particular  brick  that  may  have  been  offered 
at  any  competition,  it  will  be  necessary  to  combine  them  properly 
in  order  to  arrive  at  one  result  to  designate  the  actual  value  of  any 
particular  result. 

The  Board  of  Public  Improvements  of  St.  Louis  adopted 
formula  1,  while  Prof.  J.  B.  Johnson  advised  formula  2,  and  Mr. 
H.  A.  Wheeler  of  the  Missouri  Geological  Survey  recommends 
No.  3,  using  the  same  factors  as  in  the  other  two,  and  formula  4 
when  the  two  additional  factors  of  specific  gravity  and  hardness 
are  used. 


10         1          T'          C 
Formula  1.      r-.=  - 


2. 


. 
3.     F=18 


4. 


220   '   1000' 
fji  /"> 

220  +  1000 

325  -  D 

10 


278        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Formulas  1  and  2  are  based  on  the  following  mean  numerical  values 
deduced  from  the  St.  Louis  tests: 

R  =  16.5  per  cent; 
RG  =    4.7    "      " 
A  =    1.25  "       " 
T'  =      3300  pounds; 
C  =  13,000       " 

In  deducing  mean  values  for  formulae  3  and  4  a  study  was 
made  of  tests  from  various  parts  of  the  country,  from  which  262 
were  selected  for  use,  and  they  gave  the  following: 

R  =  8  per  cent; 
A  =2    "      " 
T  =  2200  pounds; 
C  =  10,000    " 
D  =2.25 
#=6.5 

In  which  V  =  the  required  value;  RG  =  the  rattler  loss  in  terms 
of  granite;  R  =  the  rattler  loss  in  percentage  of  the  weight  of 
the  hrick;  A  =  per  cent  of  absorption  of  the  weight  of  the  brick; 
T  =  modulus  of  rupture  per  square  inch;  T"  =  the  crushing 
strength  per  inch  width;  C  =  crushing  strength  per  square  inch; 
D  =  specific  gravity;  IT  =  hardness  by  Mohs'  scale. 

Where  the  four  factors,  R,  A,  T,  and  (7,  only  are  used,  Mr. 
Wheeler  assigns  the  value  of  60  per  cent  to  the  rattler  test  and  50 
per  cent  where  all  the  above  factors  are  known,  while  Prof.  John- 
son assigns  50  and  the  Board  of  Public  Improvements  of  St.  Louis 
only  30  per  cent.  It  is  probable  that  the  value  of  the  rattler  test 
is  of  even  greater  value  than  that  assigned  by  Mr.  Wheeler,  and 
might  reach  75  per  cent,  as  no  engineer  would  be  willing  to  lay 
any  brick  in  a  pavement  that  had  not  passed  a  good  test  in  the 
rattler. 

Mr.  Wheeler  published  a  table  in  the  book  heretofore  men- 
tioned in  which  he  shows  the  comparative  ratings  of  two  well- 
known  paving-brick  by  the  formulae  here  given,  in  which  the 
necessity  of  assigning  the  proper  percentages  to  each  factor  is  very 
clearly  demonstrated  to  any  one  having  a  knowledge  of  these 
brick. 


BRICK  PAVEMENTS.  279 

In  Columbus,  Ohio,  it  has  been  the  practice  to  take  one  or 
more  samples  from  each  street  of  all  brick  used  and  test  them  by 
the  rattler  test  as  specified  by  the  National  Brick  Manufacturers' 
Association,  calling  as  loss  by  abrasion  all  pieces  of  one  pound 
weight,  and  less,  aiming  to  admit  on  the  streets  only  such  brick 
-as  would  show  a  loss  of  less  than  27.5  per  cent  by  abrasion  under 
this  test. 

A  record  of  one  test  was  for  blocks  selected  in  order  as  deliv- 
ered by  the  contractor:  charge  No.  1,  loss  18.55  per  cent;  charge 
No.  2,  loss  17.9  per  cent — average  18.22  per  cent. 

At  the  same  time,  blocks  which  were  slightly  fire-cracked  and 
which  the  inspector  had  rejected  as  unfit  for  use  were  tested  with 
the  following  results:  charge  No.  1,  loss  25.5  per  cent;  charge 
No.  2,  loss  24.25  per  cent — average  24.87  per  cent.  Which  is  a 
somewhat  better  showing  than  was  generally  obtained,  the  best 
single  charge  being:  loss  15.4  per  cent,  average  17.07  per  cent; 
and  the  highest  being:  loss  36.65  per  cent,  average  33.56  per  cent. 

Size  of  Bricks. 

Paving-bricks  have  been  made  of  very  different  shapes  and 
sizes  by  different  manufacturers.  Other  things  being  equal,  the 
same  principles  laid  down  for  establishing  dimension  of  granite 
"blocks  would  apply  to  sizes  of  paving-bricks;  but  it  must  be  re- 
membered that  while  the  material  of  which  the  granite  blocks  arc 
made  is  natural,  that  composing  the  bricks  is  artificial.  Conse- 
quently new  conditions  arise,  and  in  determining  dimensions  con- 
sideration must  be  given  to  the  method  of  manufacture.  If  the 
brick  is  made  too  long,  it  is  liable  to  warp  either  in  the  preliminary 
drying  or  while  it  is  being  burned  in  the  kiln.  If  it  is  too  thick, 
so  that  the  clay  in  the  interior  is  vitrified  with  difficulty,  it  is 
probable  that  when  sufficient  heat  has  been  applied  to  insure 
proper  vitrification  to  the  central  part  of  the  brick,  the  outside 
will  have  been  damaged  and  the  brick  not  of  uniform  texture 
texture  throughout,  so  that  in  determining  the  thickness  the  same 
rule  will  not  apply  to  all  clays,  as  some  clays  will  vitrify  more 
readily  than  others.  But  a  thickness  must  be  adopted  for  any 
particular  clay  which  will  admit  of  complete  vitrification  at  a  tem- 
perature which  will  not  injure  any  portion  of  the  brick. 


280        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Then,  too,  apart  from  the  physical  conditions  governing  the 
size,  the  economic  reasons  must  be  considered.  If  brick  are  made 
of  an  unnatural  size  as  compared  to  building-brick,  underburned 
brick,  which  are  always  found  in  greater  or  less  extent  in  every 
kiln  of  paving-brick,  will  be  almost  a  total  loss,  as  they  can  be  used 
to  very  little  advantage  for  any  other  purpose;  while  if  of  about 
the  standard  size  of  building-brick,  the  soft  brick  can  always  be 
disposed  of  to  builders  without  loss. 

Bricks  have  been  made,  however,  and  used  in  pavements,  hav- 
ing dimensions  as  large  as  4  x  5  x  12  inches,  but  for  the  above  and 
other  reasons  their  use  has  been  discontinued,  and  at  the  present 
time  smaller  sizes  are  adopted.  Many  manufacturers  make  two 
sizes,  the  smaller  being  practically  2J  x  4  x  8-J  inches,  and  the 
larger  3x4x9  inches.  These  latter  are  generally  termed  blocks 
in  distinction  from  the  smaller  size. 

Form  of  the  Brick. 

Whether  the  bricks  should  be  made  rectangular  in  shape  or 
whether  the  corners  should  be  rounded  off  is  a  mooted  question. 
The  argument  used  by  the  advocates  of  the  round  corner  is  that 
if  the  brick  are  laid  with  square  edges,  the  impact  of  the  horses' 
shoes  soon  wears  them  off  practically  to  the  round  corners,  leav- 
ing them  in  a  rougher  and  much  worse  condition  than  if  they  had 
been  originally  made  round.  There  is  considerable  merit  in  this  ar- 
gument, and  if  the  joints  are  to  be  filled  with  sand  or  some  unstable 
filler,  it  is  probably  the  best  shape;  but  if  the  joint-filler  is  rigid, 
like  Portland  cement  or  some  similar  filler,  so  that  the  joints 
can  be  filled  solidly  to  the  top  and  so  maintained,  it  would  seem 
that  the  square-edged  brick  would  give  better  results.  With  the 
rounded  corner  and  the  joints  filled  only  to  the  top  of  the  brick  a 
thin  edge  of  the  filler  must  be  made  at  each  side  of  the  joint,  which 
is  maintained  with  difficulty  under  traffic.  It  has  not  been 
definitely  determined  by  manufacturers  which  is  the  better 
method. 

Different  devices  have  been  adopted  for  keeping  the  bricks  at 
a  certain  distance  from  each  other  in  a  pavement,  so  that  the  space 
may  be  left  sufficiently  wide  to  admit  of  enough  filling  material  to 
make  a  good  and  substantial  joint.  Some  blocks  have  a  projection 


t  ,   ' 

BRICK  PAVEMENTS.  281 

on  one  side  to  maintain  the  distance,  and  a  groove  on  the  other 
side  to  receive  the  joint-filling  material.  It  is  a  well-known  fact 
that,  whatever  the  material  composing  blocks  for  pavements,  the 
smaller  the  amount  of  joint-space  the  better.  It  would  seem, 
therefore,  that  it  was  hardly  necessary  to  provide  any  special  ar- 
rangement for  keeping  the  brick  apart.  It  has  been  the  author's 
experience  that  where  the  brick  were  apparently  laid  tight  in  the 
work,  when  they  came  to  be  rammed  or  rolled  sufficient  space 
would  be  found  to  receive  the  proper  amount  of  joint-filler.  Upon 
this  question  of  size  and  shape  the  Philadelphia  specifications  say: 

"  The  bricks  or  blocks  must  be  vitrified  clay,  repressed, 
especially  burned  for  street-paving,  and  not  less  than  9  inches 
long,  4  inches  wide,  and  3  inches  thick.  The  bricks  or  blocks  must 
have  two  or  more  ribs  or  projections  upon  one  of  the  vertical  sides 
extending  from  top  to  bottom.  On  the  opposite  vertical  side  of 
the  brick  or  block  [there  should  be]  a  groove  or  channel  extend- 
ing longitudinally  from  end  to  end  of  the  brick  or  block,  and  con- 
necting with  the  like  transverse  groove  extending  across  each  end, 
thus  serving  by  contact  with  the  flat  side  of  an  adjoining  brick  or 
block  to  secure  a  separation,  so  that  cementing  material  may  effect 
a  practical  encircling  of  each  brick  or  block,  flowing  into  the 
grooves,  thus  keying  or  locking  together  the  entire  pavement. 
The  Department  of  Public  Works  is  authorized,  however,  to  ac- 
cept proposals  for  street-paving  with  other  vitrified  brick,  pro- 
vided they  shall  be  in  quality  not  inferior  to  those  herein 
described." 

St.  Louis  specifications  say:  "  The  brick  shall  not  be  less  than 
8  inches  nor  more  than  9  inches  long,  not  less  than  2J  inches  nor 
more  than  4  inches  wide,  not  less  than  4  inches  nor  more  than  4^ 
inches  deep,  with  rounded  edges  of  a  radius  of  f  of  an  inch.  Said 
brick  shall  be  of  the  kind  known  as  repressed  brick,  and  shall  be. 
repressed  to  produce  a  mass  free  from  internal  flaws,  cracks,  or 
laminations." 

Foundation. 

The  foundation  of  a  brick  pavement,  like  that  of  all  others, 
is  very  important.  As  has  been  shown  before,  blocks  of  any 
kind  wearing  from  abrasion  wear  much  more  rapidly  if  they  are 


28:3        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

not  exactly  level.  Thus  if  the  blocks  are  set  and  maintained  with 
a  smooth  even  surface,  so  that  the  wear  is  directly  on  the  top 
rather  than  on  the  edges  or  corners,  the  abrasion  is  reduced  to  a 
minimum  and  the  life  of  the  pavement  correspondingly  increased. 
This  is  particularly  important  in  a  brick  pavement,  because  the 
blocks  are  necessarily  small  and  the  number  of  joints  and  corners 
correspondingly  increased,  so  that  to  get  the  best  results  the 
foundation  should  be  such  as  will  allow  the  brick  to  be  placed  in 
position  and  ^so  maintained  under  traffic.  Unfortunately  for  the 
good  name  of  brick  pavements  this  principle,  if  understood,  has 
not  always  been  carried  out  in  practice. 

Brick  pavements  have  been  laid  upon  foundations  of  sand 
alone,  a  combination  of  boards  and  sand,  a  combination  of  sand 
and  bricks  laid  flat,  and  on  a  foundation  of  broken  stone  and 
cement  concrete. 

For  reasons  specified  above,  it  can  readily  be  understood  that 
a  foundation  of  sand  alone  cannot  be  expected  to  give  good  re- 
sults. The  weight  of  a  vehicle  coming  upon  any  particular  brick 
is  transferred  to  the'  foundation  beneath,  and  if  the  foundation 
be  sand,  and  the  underlying  earth  unstable,  any  amount  of  heavy 
traffic  is  bound  to  make  such  pavement  soon  appear  rough  and 
uneven.  The  wear  then  quickly  becomes  abnormal,  and  the  pave- 
ment wears  out  and  is  replaced  long  before  it  should  have  been. 
The  early  pavements  in  some  places  were  laid  on  a  foundation  of 
3  inches  of  sand,  upon  which  were  placed  oak  boards  1J  inches 
thick  which  had  been  previously  soaked  in  coal-tar,  and  this  cov- 
ered with  a  cushion-coat  of  1  inch  or  1J  inches  of  sand.  This 
foundation  gave  very  good  results  for  light  traffic,  but  could  not 
be  expected  to  sustain  the  heavy  travel  of  business  streets. 

Another  method  adopted  was  laying  the  bricks  flatwise  on  a 
bed  of  sand,  rolling  and  ramming  them  thoroughly.  They  were 
then  covered  with  a  cushion-coat  of  sand,  and  the  surface  brick 
set  on  edge.  This  construction  has  been  used  to  considerable  ex- 
tent in  the  Central  West  and  with  good  results.  It  commends 
itself  to  cities  located  at  any  distance  from  stone-quarries,  for 
two  reasons:  the  stone  necessary  for  this  foundation,  whether 
used  with  or  without  cement,  is  expensive,  and  because  it  gives 
an  opportunity  for  the  economical  use  of  the  underburned  brick, 


BRICK  PAVEMENTS.  283 

which  are  not  suitable  for  the  wearing  surface,  but  have  been 
burned  sufficiently  to  give  satisfaction  in  the  lower  course.  It 
can  be  seen  that  in  a  locality  where  brick  are  readily  available 
and  the  cost  of  freight  is  correspondingly  low,  and  where  broken 
stone  is  expensive,  this  would  be  an  economical  foundation;  but 
if  the  brick  are  to  be  carried  to  such  a  distance  that  freight  is  an 
important  item,  it  might  prove  to  be  expensive.  The  proper  plan 
must  be  determined  upon  in  each  case. 

Broken  Stone. 

In  many  parts  of  Illinois  where  paving-brick  have  been  used 
to  a  considerable  extent,  limestone  can  be  obtained  easily  and 
cheaply.  Consequently  foundations  of  broken  stone,  thoroughly 
rolled  and  compacted,  have  been  used  in  many  cities  with  excel- 
lent results.  With  this  material,  however,  care  must  be  taken  to 
roll  and  compact  the  stone  thoroughly  to  a  hard,  firm  surface,  so 
that  when  the  cushion-coat  of  sand  is  applied  and  the  pavement 
laid,  the  traffic  will  not  cause  the  sand  to  mix  with  the  stone  in 
the  foundation,  thus  causing  a  settlement  in  the  pavement  and 
allowing  it  to  become  rough  and  uneven.  Several  brick  pavements 
have  failed  from  this  cause.  If,  however,  the  stone  be  rolled  as 
for  a  macadam  road  and  thoroughly  compacted  and  made  solid,  it 
cannot  fail  to  give  good  satisfaction  if  undisturbed. 

Cement  Concrete. 

The  best  foundation,  although  its  expense  in  every  case  may 
not  be  justifiable,  is  cement  concrete,  such  as  has  been  heretofore 
described.  It  should  be  made  in  the  same  manner  as  for  asphalt 
or  stone,  but  care  should  be  taken  to  have  the  surface  as  smooth 
as  possible,  so  that  there  will  be  no  danger  of  any  brick  resting 
upon  a  projecting  piece  of  stone  and  so  getting  an  unequal  bear- 
ing, and  perhaps  breaking  under  a  heavy  load.  The  object  of  the 
.  sand  cushion  is  simply  to  give  the  brick  a  firm  bearing,  and  the 
smoother  the  surface  of  the  concrete  the  smaller  the  quantity  of 
sand  necessary,  and  the  smaller  the  quantity  of  sand  the  less 
liable  is  any  individual  brick  to  settle  out  of  place. 


284:        STREET  PAVEMENTS  AND  PA  VINO  MATERIALS. 

Fig.  17  represents  a  cross-section  of  a  brick  pavement  on  a  con- 
crete base. 


FIG.  17. 

Joint-filling. 

The  material  for  filling  the  joints  of  the  brick  pavement  is 
practically  the  same  as  that  used  for  stone,  with  the  exception  of 
gravel  combined  with  tar.  All  have  been  used  in  different  sec- 
tions of  the  country,  but  it  is  not  yet  a  settled  fact  which  is 
the  best.  The  City  Engineer  of  Minneapolis  in  his  report  for 
1898  states  that  when,  during  the  year,  the  city  asked  for  bids 
from  manufacturers  for  furnishing  paving-brick,  with  a  guarantee 
of  fifteen  years,  allowing  the  bidders  to  designate  the  filler  which 
they  preferred  should  be  used,  one  bidder  specified  sand,  and  dis- 
tinctly stated  that  unless  it  were  used  he  would  not  guarantee  his 
brick.  It  is  generally  considered,  however,  that  when  brick  are 
laid  on  a  solid  foundation,  a  rigid,  or  at  least  water-tight,  joint- 
filler  should  be  used.  Of  these,  the  three  principal  ones  are  Port- 
land-cement grout,  Murphy  grout,  and  paving-cement.  Engineers, 
however,  do  not  agree  as  to  which  one  of  these  gives  the  best  re- 
sults. The  two  former  are  rigid,  and  when  the  joints  are  once 
broken  they  can  never  be  made  tight  and  are  no  better  than  a  sand 
joint,  while  a  pitch  joint  once  broken  will  become  solid  again  at  a 
warmer  temperature. 

At  a  meeting  of  the  American  Society  of  Municipal  Improve- 
ments, held  in  Toronto  in  1899,  it  was  stated  by  one  engineer,  in  a 
discussion  upon  this  subject,  that  he  had  examined  nearly  all  of 
the  brick  pavements  laid  in  this  country  with  a  Portland-cement 
joint,  and  had  come  to  the  conclusion  that  they  were  failures. 
Further  on  in  the  discussion  another  engineer  of  equal  experience 
stated  that  it  was  his  belief  that  a  brick  pavement  well  laid  with 
a  Portland-cement  joint  would  last  five  years  longer  than  a  similar 
pavement  laid  with  sand  joints.  This  testimony  was  corroborated 
by  that  of  another  engineer  of  considerable  experience.  The  prin- 


BRICK  PAVEMENTS.  285 

cipal  objection  that  is  made  to  the  use  of  the  cement-grout  joint 
is  on  account  of  the  rumbling  noise  that  is  heard  when  driving  over 
such  a  pavement.  This  does  not  always  happen,  but  has  occurred 
in  a  great  many  instances  and  is  certainly  very  objectionable.  The 
rumbling  must  be  caused  by  cavities  that  exist  between  the  brick 
and  the  concrete.  Just  what  causes  these  cavities  is  not  so  well 
known. 

In  discussing  this  subject  in  a  convention  of  the  National  Brick 
Manufacturers'  Association,  held  in  Pittsburg  in  1898,  it  was 
thought  by  many  of  the  manufacturers  that  these  cavities  were 
caused  by  a  slight  shrinkage  of  the  concrete,  and  their  remedy 
was  not  to  have  the  brick  laid  until  the  cement  had  become  thor- 
oughly set  and  dry.  Other  people,  and  perhaps  those  who  have 
studied  the  question  more,  think  it  is  caused  by  expansion;  that  the 
curbstones  acting  as  abutments  support  the  arched  pavement,  and 
that  it  expands  with  the  heat  and  rises  from  the  concrete.  To 
obviate  this  it  was  recommended  that  an  expansion-joint  of  1  inch 
or  1J  inches  be  left  next  the  curb  and  filled  with  asphalt  or  paving- 
cement;  also  to  lay  expansion-joints  filled  with  the  same  material 
across  the  street  at  regular  intervals.  It  would  seem,  however,  that 
if  this  trouble  was  caused  by  expansion,  it  would  have  taken  place 
longitudinally  along  the  street,  as  the  width  of  the  street  is  slight 
as  compared  to  its  length.  This  has  occurred  in  one  or  two  in- 
stances. It  is  reported  that  at  Easton,  Pa.,  when  the  temperature 
was  94°  in  the  shade,  a  brick  pavement  was  heaved  to  such  an 
extent  that  it  broke  with  a  loud  noise.  The  rupture  formed  an 
arch  with  a  nine-foot  span  and  an  eight-inch  rise  extending  from 
•curb  to  curb,  a  distance  of  42  feet. 

An  occurrence  somewhat  similar  to  this  took  place  in  Newark, 
N.  J.  Very  few  instances,  however,  have  been  reported,  and  in 
Brooklyn,  N".  Y.,  there  is  one  street  laid  continuously  with  brick 
with  a  Portland-cement  joint,  a  distance  of  £  mile,  where  no  trouble 
of  this  kind  has  occurred. 

In  1895,  however,  two  blocks  of  brick  pavement  were  laid 
with  the  Mack  block  and  Portland-cement  joint.  After  the  bricks 
were  laid  and  had  been  rolled,  the  weather  turned  so  cold  that  it 
was  impossible  for  a  while  to  do  the  grouting.  When  the  weather 
became  warmer,  in  attempting  to  roll  further,  it  was  found  that 


286        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

the  bricks  were  so  solidly  imbedded  in  the  frozen  sand  that  many 
of  them  broke  under  the  roller  and  the  rolling  was  discontinued. 
An  attempt  was  made  to  thaw  out  the  frozen  sand  with  hot  water, 
but  how  thoroughly  it  was  accomplished  is  uncertain.  After  the 
pavement  had  been  laid  for  some  time,  a  great  deal  of  rumbling 
was  observed  when  teams  were  driving  over  it,  and  many  com- 
plaints were  made  by  property  owners.  The  bricks  were  cut  out 
for  a  distance  of  1^  inches  along  the  curb  on  both  sides,  to  see  if 
that  would  relieve  it,  but  no  difference  was  noticed.  A  fifteen-ton 
macadam  roller  was  run  continuously  over  one  block  during  an 
entire  day  in  an  attempt  to  press  the  brick  down  to  a  firm,  bearing. 
This  caused  no  impression  whatever  upon  the  pavement,  and  the 
noise  still  continued  as  loud  as  before.  So  many  and  persistent 
were  the  complaints  that  the  brick  was  finally  taken  up  and  re- 
placed with  asphalt.  The  other  block,  however,  was  not  quite  so 
noisy  and  is  still  in  use,  and  no  complaints  are  made  by  the  prop- 
erty owners,  and  it  seems  as  if  the  noise  had  decreased. 

The  theory  of  the  city  authorities  was  that  there  were  slight, 
local  cavities  existing  between  the  brick  and  the  concrete,  caused 
by  the  frozen  sand  melting  and  shrinking  somewhat.  It  is  prob- 
able that  an  air-space  of  -J  of  an  inch,  and  perhaps  even  less  than 
that,  would  cause  this  rumbling,  and  it  would  seem  in  this  case  as 
if  the  above  were  the  proper  solution.  The  argument  against  the 
expansion  theory  is  that  in  many  cases  the  noise  is  reported  to  have 
been  greater  during  cold  weather  than  warm. 

There  seems  to  be  no  question  but  that  a  brick  pavement  with 
its  joints  filled  with  a  good  cement  grout  will  last  materially  longer 
than  one  with  a  less  rigid  filler,  and  if  the  pavement  is  laid  during 
warm  weather  and  care  is  taken  to  have  the  bricks  thoroughly  rolled 
and  bedded  in  sand,  there  should  be  no  trouble  from  abnormal 
noise.  No  trouble  from  noise  has  ever  been  experienced  when 
sand  or  paving-cement  has  been  used  as  a  filler.  If  the  foundation 
is  not  solid  and  is  liable  to  settle  unevenly,  it  would  be  a  waste  of 
money  to  use  a  rigid  filler. 

One  objection  to  the  rigid  joint  is  the  difficulty  with  which  cuts- 
are  made  in  the  pavement.  Many  bricks  are  broken  in  taking  them 
up,  and  the  expense  of  cleaning  before  relaying  is  considerable. 


BRICK  PAVEMENTS.  287 

It  is  also  hard  to  keep  traffic  off  a  small  patch  while  the  cement  is 
setting. 

A  very  large  proportion  of  the  brick  pavements  in  the  West 
have  been  laid  entirely  with  sand  joints,  and  experience  there  has 
shown  that  good  brick  will  wear  well  under  such  conditions,  but  the 
pavement  will  not  be  impervious  to  water.  When  that  is  required 
a  solid  filler  must  be  used;  and  if  the  engineers  are  afraid  of  noise 
from  Portland-cement,  a  paving-cement  filler  can  be  used  to 
advantage.  If  sand  is  used,  it  should  be  fine,  silicious,  and  per- 
fectly dry,  so  that  it  can  be  swept  readily  into  the  joints,  so  as  to 
fill  them  completely  and  thus  maintain  the  bricks  in  the  position 
in  which  they  are  placed. 

The  paving-cement  should  be  applied  at  a  temperature  of  from 
250°  to  300°,  and  if  possible  during  the  warm  portion  of  the  day 
when  the  bricks  themselves  are  warm,  so  as  to  allow  the  cement  to 
flow  readily  and  completely  fill  the  joints.  This  filling  is  some- 
times applied  by  pouring  the  cement  directly  into  the  joints  from 
buckets  made  for  that  purpose,  or  by  spreading  it  indiscriminately 
over  the  surface  and  sweeping  it  into  the  joints  with  brooms.  The 
objection  to  this  latter  method  is  that  a  certain  amount  of  the 
cement  is  wasted  and  the  entire  surface  of  the  pavement  covered, 
which  is  liable  to  be  sticky  during  the  hottest  part  of  the  day.  To 
obviate  this  last  trouble,  as  soon  as  the  joints  are  filled  the  pave- 
ment should  be  covered  with  a  thin  coating  of  sand,  which  under 
traffic  will  take  up  the  cement  and  clean  the  surface  to  a  certain 
extent.  If  the  first  covering  should  not  do  this  satisfactorily,  a 
second  can  be  applied.  This  will  also  probably  be  necessary  if  the 
joints  are  filled  from  the  buckets. 

The  grout,  when  Portland  cement  is  used,  is  made  by  mixing 
equal  parts  of  Portland  cement  and  fine,  sharp  sand  with  sufficient 
water  to  give  it  such  a  consistency  that  it  will  readily  flow  into  all 
the  joints.  Great  care  is  necessary  in  this  mixing  both  of  the 
cement  and  sand,  and  also  when  the  water  is  added,  so  that  the 
grout  shall  be  uniform  in  quality  and  not  leave  one  joint  in  the 
bricks  filled  with  almost  pure  cement  and  another  with  almost  clear 
sand.  The  grout  is  generally  mixed  in  large  boxes,  taking  one 
barrel  of  cement  at  a  time,  and,  after  being  thoroughly  mixed, 
poured  out  upon  the  pavement  and  thoroughly  broomed  into 


288        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

the  joints.  The  street  should  be  closed  to  traffic  until  the 
mortar  of  the  joints  is  absolutely  and  entirely  set,,  which  will 
probably  require  a  week  and  perhaps  more;  but  it  is  very  important 
that  it  be  thoroughly  hardened  before  any  traffic  is  allowed  upon  it. 

Laying  the  Brick. 

After  the  concrete  has  become  sufficiently  set  it  should  be 
covered  with  a  sand  cushion,  care  being  taken  to  see  that  the  sand 
is  entirely  free  from  any  small  stones  or  pebbles  that  might  cause 
the  brick  to  be  supported  unequally.  The  sand  is  brought  to  the 
exact  shape  desired  by  means  of  a  template  which  has  been  cut  to 
the  required  crown,  resting  on  the  curbs  if  the  roadway  be  nar- 
row, or,  if  too  wide  for  that  method,  with  one  end  resting  on  the 
curb  and  the  other  on  a  scantling  buried  in  the  sand  at  the  cen- 
tre. After  one  side  is  brought  to  the  desired  shape  the  template 
can  be  reversed  and  used  on  the  other  side.  No  walking  on  the 
prepared  surface,  or  disturbance  of  it  of  any  kind,  should  be  al- 
lowed. The  pavers,  unlike  stone-pavers,  should  stand  on  the 
completed  pavement,  working  from  themselves.  The  courses 
should  always  be  started  with  a  half-brick,  so  as  to  break  the 
joints  evenly  across  the  street,  and  when  finished  they  should  be 
set  up  tightly  with  an  iron  bar  so  that  the  end  joint  shall  be  as 
close  as  possible.  • 

This  is  important,  whatever  the  joint-filler  is,  as  these  cross- 
joints  come  directly  in  the  line  of  travel.  The  courses  should  be 
kept  square  with  the  street  and  trued  up  every  four  or  five  feet. 
It  is  customary  generally  to  have  one  man  working  at  the  side  of 
a  street  where  the  courses  are  completed,  cutting  the  brick  to  be 
used  as  closers.  After  the  brick  have  been  laid,  the  surface  should 
be  swept  off  clean  and,  if  a  steam-roller  is  to  be  had,  should  be 
thoroughly  rolled  until  all  the  brick  are  brought  to  a  firm  and 
even  bearing.  If  the  brick  run  unevenly  for  hardness,  it  may  be 
desirable,  just  previous  to  rolling,  to  wet  the  pavement  thoroughly 
with  a  hand-hose,  so  that  the  soft  bricks  can  be  detected.  This  is 
a  sure  test,  as  the  soft  brick  absorb  the  water  readily,  and  when 
the  harder  ones  dry  those  retaining  the  moisture  can  easily  be  seen 
and  should  be  removed  and  others  put  in  their  places. 

If  a  steam-roller  cannot  be  had,  good  results  can  be  obtained 


BRICK  PAVEMENTS.  289 

by  ramming,  when  a  plank  should  be  laid  on  the  surface  parallel 
to  the  curb-lines,  and  the  pavement  rammed  by  striking  the  plank 
with  an  iron  rammer.  If  the  planking  is  used  crosswise  of  the 
street,  the  pavement  is  liable  to  be  rammed  unevenly.  The  prin- 
ciples laid  down  in  the  stone  pavement  for  the  position  of  the 
bricks  and  direction  of  the  courses,  both  between  streets  and  at 
intersections,  are  perfectly  applicable  to  brick.  The  method 
shown  in  Fig.  57,  called  the  herringbone  plan,  is  sometimes  used. 
This,  however,  is  not  desirable,  as  between  the  streets  it  brings  the 
line  of  cross-joints  lengthwise  to  the  travel  of  the  street,  which 
permits  a  weak  spot  in  the  pavement,  and  at  intersections  it  brings 
a  great  many  of  the  brick  lengthwise  of  the  traffic  turning  the 
corners.  This  method  has  never  been  used  to  any  great  extent. 
Brick  pavements,  especially  when  laid  with  a  sand  filler,  generally 
show  considerable  wear  during  the  first  few  weeks,  especially  if 
laid  with  rectangular  bricks  rather  than  those  with  rounded  ejlges. 
This  is  because  the  traffic  quickly  finds  any  inequalities  in  the  sur- 
face, and  also  because  the  horses'  shoes  soon  round  off  the  edges  of 
the  softer  brick;  but  in  a  short  time  this  abnormal  wear  ceases, 
and  from  then  on  the  observable  wear  is  slight. 

Brick  specifications  vary  principally  in  the  tests  that  shall  be 
required,  joint-filling,  and  foundations.  The  following  is  taken 
from  the  specifications  of  St.  Louis: 

"  To  secure  uniformity  in  bricks  of  approved  manufacture,  de- 
livered for  use,  the  following  tests  shall  be  made: 

"  1.  They  shall  show  a  modulus  of  rupture  in  cross-breaking  of 
not  less  than  twenty-five  hundred  pounds  per  square  inch. 

"  2.  Specimen  bricks  shall  be  placed  in  the  machine  known  as 
a  (  rattler,'  twenty-eight  inches  in  diameter,  making  thirty  revo- 
lutions per  minute.  The  number  of  revolutions  for  a  standard 
test  shall  be  eighteen  hundred,  and  if  the  loss  of  weight  by 
abrasion  or  impact  during  such  test  shall  exceed  thirty  per  cent 
of  the  original  weight  of  the  bricks  tested,  then  the  bricks  shall 
be  rejected.  An  official  test  to  be  the  average  of  two  of  the  above 
tests. 

"  No  bid  contemplating  the  use  of  rejected  brick  shall  be  enter- 
tained. 

"  Samples  may  be  submitted  by  manufacturers,  in  which  case 


290        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

the  bidder  proposing  to  use  brick  of  such  manufacture  will  not  be 
required  to  submit  samples.  The  quality  of  brick  furnished  must 
conform  to  the  samples  presented  by  the  manufacturers  and  kept 
in  the  office  of  the  Street  Commissioner. 

"  The  Street  Commissioner  reserves  the  right  to  reject  any  and 
all  bricks  which,  in  his  opinion,  do  not  conform  to  the  above  speci- 
fications. 

"  Any  brick  may  have  a  proper  shrinkage,  but  shall  not  differ 
materially  in  size  from  the  accepted  samples  of  the  same  make,  nor 
shall  they  differ  greatly  in  color  from  the  natural  color  of  the 
well-burned  brick  of  its  class  and  manufacture. 

"  No  bats  or  broken  bricks  shall  be  used  except  at  the  curbs, 
where  nothing  less  than  half  a  brick  shall  be  used  to  break  joints. 
The  bricks  to  be  laid  in  straight  lines,  and  all  joints  broken  by  a 
lap  of  at  least  two  inches,  to  be  set  on  edge  on  the  sand  as  closely 
and  compactly  as  possible  and  at  right  angles  with  the  line  of  the 
curb,  except  at  street-intersections,  where  they  are  to  be  laid  as 
the  Street  Commissioner  may  direct. 

"  The  pavement  to  be  thoroughly  rammed  two  or  three  times 
with  a  paver's  rammer  weighing  not  less  than  seventy-five  pounds. 
The  pavement  to  be  surfaced  up  by  using  a  long  straight-edge  and 
by  a  thorough  rolling  of  the  pavement  with  a  road-roller  weigh- 
ing not  less  than  three  nor  more  than  six  tons,  and  when  com- 
pleted to  conform  to  the  true  grade  and  cross-section  of  the  road- 
way. 

"  All  joints  in  the  pavement  shall  be  completely  filled  with 
Portland-cement  grout.  The  cement  to  be  of  brand  approved  by 
Street  Commissioner,  to  be  fine  ground;  eighty-five  per  cent  shall 
pass  through  a  sieve  having  ten  thousand  meshes  to  the  square 
inch.  All  cement  shall  be  capable  of  withstanding  a  tensile  strain 
of  five  hundred  pounds  per  square  inch  of  section,  when  mixed 
neat,  made  into  briquettes  and  exposed  twenty-four  hours  in  air 
and  six  days  under  water.  All  cement  shall  be  put  up  in  well- 
made  barrels,  and  all  short  weight  or  damaged  barrels  will  be  re- 
jected. Cement  without  manufacturers'  brand  and  other  certifi- 
cate will  be  rejected  without  test." 

"  The  grout  shall  be  mixed  in  portable  boxes  in  the  proportion 
of  one  part  cement  to  one  part  sand.  The  cement  and  sand  to  be 


BRICK  PAVEMENTS.  291 

thoroughly  mixed  together  dry,  then  sufficient  water  to  be  added 
to  make  a  grout  of  proper  fluidity  when  thoroughly  stirred. 

"  The  grout  shall  be  transferred  to  the  pavement  in  hand- 
scoops,,  or  as  the  Street  Commissioner  may  direct,  and  rapidly 
swept  into  the  joints  of  the  pavement  with  proper  brooms. 

"  Teams,  carts,  and  wagon  traffic  and  wheeling  in  barrows,  ex- 
cept on  plank,  will  not  be  allowed  on  the  pavement  for  at  least 
seven  days  after  the  grout  is  applied. 

"  The  surface  of  the  pavement,  when  completed,  shall  be  cov- 
ered with  one-half  inch  of  clean,  coarse  sand  of  approved  quality, 
which,  with  all  dirt,  shall  be  removed  from  the  pavement  and 
sewer-inlets,  by  or  at  the  expense  of  the  contractor,  at  such  time, 
before  the  final  acceptance  of  the  work,  as  the  Street  Commis- 
sioner may  direct." 

The  following  are  extracts  from  the  Philadelphia  specifications: 

"  The  bricks  or  blocks  must  be  set  vertically  on  edge  in  close 
contact  with  each  other,  in  straight  rows  across  the  street  excepting 
at  intersections,  which  shall  be  paved  at  an  angle  of  forty-five  de- 
grees to  the  lines  of  the  intersecting  roadways,  and  those  in  adjoin- 
ing rows  so  set  as  to  regularly  break  joints.  No  bats  or  broken 
bricks  or  blocks  can  be  used  except  at  curbs,  where  half-bricks  or 
blocks  must  be  used  to  break  joints.  The  bricks  or  blocks,  having 
been  set,  must  be  rolled  with  the  above-mentioned  steam-roller. 

"  After  being  rolled,  the  surface  of  the  roadway  must  be  true 
to  grade,  and  show  no  continuous  lines  of  unequal  settlements  pro- 
duced by  the  roller. 

"  After  being  thoroughly  rolled,  the  bricks  or  blocks  shall  be 
grouted  with  Portland-cement  grouting  until  the  joints  are  filled 
flush  with  the  surface  of  the  bricks  or  blocks.  The  grouting  to  be 
composed  of  one  part  fresh-ground  Portland  cement  and  one  part 
clean  bar  sand,  and  mixed  with  clean  water  to  a  consistency  that 
will  readily  permeate  the  joints  between  the  bricks." 

While  brick  pavements  have  been  in  use  in  this  country  for 
only  about  twenty  years,  according  to  the  bulletin  of  the  Depart- 
ment of  Labor  issued  in  1899  there  were  18,665,000  square  yards 
in  cities  having  over  thirty  thousand  inhabitants,  Philadelphia 
liaving-  the  most,  with  1,777,123  square  yards,  Des  Moines,  la., 
being  next,  with  1,509,195  square  yards,  Columbus,  0.,  third,  with 


STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

1,505,015  square  yards,  Cleveland,  0.,  with  800,000  square  yards, 
and  Louisville,  Ky.,  with  659,733  square  yards. 

The  following  are  the  lowest  bids  received  for  brick  pavements 
at  different  places  in  the  spring  of  1900: 

Hampton,  Va.,  May  3 $2.25 

Olean,  N.  Y.,  April  25 1.80 

Norfolk,  Va.,  April  25 2.17 

Bellefontaine,  O.,  April  24 1.36 

Paterson,  N.  J.,  April  16 2.10 

Gloversville,  N.  Y.,  April  16 1.45 

Columbus,   Ga 2.00 

Rome,  N.  Y.,  May  9 1.79% 

Cohoes,  N.  Y.,  May  9 2.47 

New  Haven,  Conn.,  May  18 1.92 

Cambridge,  O.,  June  2 1.15 

Binghamton,  N.  Y 1.95 

Glens  Falls,  N.  Y 1.91 

Bay  City,  Mich 1.76 

Peoria,   111 1.3234 

Bridgeport,   Conn 2.19 

MATERIAL    PER    SQUARE    YARD    OF    BRICK    PAVEMENT. 

Size  of  brick 2y2  X  4  X  8y2  inches 

Size  of  blocks 3      X4x9      inches 

Number  of  brick  per  square  yard 58 

Number  of  blocks 44 

Yards  of  pavement  per  barrel  of  Portland  cement 

for  joint-filling 45 

Gallons  paving-cement  per  square  yard 1% 

ESTIMATED    COST. 

58  bricks  at  $14  per  M $0.81 

Joint-filling  Portland  cement 10 

Joint-filling  paving-cement 16 

Sand    : 05 

Labor  laying 06 

Concrete  base 55 

Total  Portland-cement  joints $1.57 

Total  paving-cement  joints $1.63 


CHAPTER  X. 

WOOD    PAVEMENTS. 

WITHOUT  doubt  the  crudest  and  probably  the  earliest  form  of 
a  wooden  roadway  was  that  which  is  generally  known  as  the 
corduroy  road.  This  was  constructed  roughly  by  laying  logs  cut 
to  the  desired  length  across  the  roadway  in  close  contact  with  each 
other.  This  construction  was  used  at  low  places  in  roads  across 
swamps,  and,  while  being  very  rough  and  uncomfortable,  was  fairly 
serviceable  and  made  many  of  the  roads  passable  which,  without 
this,  could  not  have  been  used  for  a  considerable  portion  of  the 
year.  This  form  of  roadway  is  in  use  now  to  a  limited  extent  on 
wood  roads  in  certain  parts  of  New  England. 

In  Alpena,  Mich.,  roadways,  and  even  entire  streets,  have  been 
graded  with  sawdust,  while  in  other  parts  of  the  State  roads  have 
been  constructed  of  charcoal.  The  method  was  to  pile  logs  along 
the  road  two  or  three  feet  high,  and  burn  them  in  practically  the 
position  in  which  the  material  was  to  be  used.  After  the  coal  was 
burned,  it  was  raken  off  and  graded  down  to  the  required  width  and 
depth  of  the  road.  This  construction  gave  very  good  satisfaction, 
and  in  1845  the  Commissioner  of  Patents  in  his  report  stated  that 
at  the  season  when  the  mud  in  an  adjoining  road  was  half-axletree 
deep,  on  the  coal  road  there  was  none  at  all,  and  the  impress  of 
the  feet  of  horses  passing  rapidly  over  it  was  like  that  made  on 
hard-washed  sand  as  the  surf  recedes  on  the  shore  of  a  lake. 

Russia,  however,  is  reported  to  have  had  the  first  real  wooden 
pavements,  as  hexagonal  blocks  are  said  to  have  been  in  use  there 
several  hundred  years  ago.  They  could  not  have  been  used  to  any 
great  extent  or  for  any  great  length  of  time,  as  no  detailed  record 
is  obtainable  of  them. 

In  .London,  Eng.,  the  first  wooden  pavement  was  laid  in  1839. 


294        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

This  consisted  of  hexagonal  blocks  of  fir,  some  6  to  8  inches 
across  and  4  to  6  inches  deep.  They  were  laid  on  a  foundation  of 
gravel  that  had  been  previously  compacted.  The  blocks  were  either 
bevelled  on  the  edges  or  grooved  on  the  face  to  afford  foothold  for 
the  horses.  These  first  pavements  were  not. very  successful,  but 
others  soon  followed.  Mr.  Hayward,  the  engineer  of  the  Sewer 
Commission,  stated  in  a  report  made  in  1874  that,  counting  the  size 
of  blocks  as  constituting  the  difference,  there  must  have  been  more 
than  two  dozen  different  kinds  of  wood  pavements  experimented 
with  in  the  city  previous  to  that  time. 

Another  system  known  as  Carey's  consisted  of  blocks  6J  to  7-| 
inches  wide,  13  to  15  inches  long,  and  8  or  9  inches  deep,  the  sides 
and  ends  having  projecting  and  re-entering  angles,  locking  the 
blocks  together  to  prevent  unequal  settlement.  Pavements  of  this 
kind  were  laid  in  1841  and  1842.  They  required  renewing  every 
three  or  four  years.  The  dimensions  of  the  blocks  were  afterwards 
modified  and  finally  reduced  to  a  width  of  4  inches  and  a  depth  of 
5  or  6  inches,  and  the  re-entering  angles  were  also  discarded. 

Another  system,  known  as  Improved  Wood,  was  first  adopted 
in  1871.  On  a  subgrade  a  bed  of  4  inches  of  sand  was  laid,  and 
upon  that  two  layers  of  inch  deal  boards,  saturated  with  boiling 
tar,  one  layer  across  the  other.  The  blocks  were  3  inches  wide,  5 
inches  deep,  and  9  inches  long.  They  also  were  dipped  in  tar  and 
laid  on  the  boards  with  the  end  joints  closed,  but  the  transverse 
joints  were  f  of  an  inch  wide,  the  space  being  maintained  by  pieces 
of  boards  nailed  to  the  foundation  and  also  to  the  blocks.  The 
joints  were  filled  with  gravel,  rammed,  then  a  composition  of  pitch 
and  tar  was  poured  in  until  the  joints  were  completely  filled,  when 
the  surface  was  also  covered  with  tar,  gravel,  and  sharp  sand. 
This  foundation  was  somewhat  elastic  and  maintained  the  even 
surface  of  the  pavement  as  long  as  it  was  in  shape,  but  when  the 
pavement  became  pervious  to  water  it  settled  and  became  rough 
and  uneven.  This  was  probably  the  first  use  of  the  tar  and  gravel 
joint  for  pavements  of  any  description. 

In  1872  a  cement-concrete  foundation  was  first  used  for  a  wood 
pavement.  The  concrete  was  4  inches  thick  and  was  laid  by  the 
Ligno  Mineral  Co.  The  blocks  were  of  beech,  mineralized  by  a 
special  process,  3J  inches  wide,  4J  inches  deep,  and  7J  long,  with 


.       WOOD  PAVEMENTS.  295 

the  ends  cut  to  an  angle  of  60°.  They  were  laid  with  the  ends 
inclining  in  opposite  directions  in  alternate  courses.  In  a  few 
jears,  however,  this  form  of  block  was  abandoned  for  the  rectangu- 
lar, and  fir  was  used  instead  of  beech.  The  blocks  were  bedded 
in  Portland  cement  and  laid  with  joints  J  inch  wide,  partly  filled 
with  asphalt,  and  then  grouted  with  mortar.  It  was  thought  after 
a  few  years'  experience  that  the  laying  of  the  blocks  directly  upon 
concrete  made  so  rigid  a  construction  that  the  blocks  wore  more 
rapidly  under  traffic  than  they  otherwise  would.  There  were  sev- 
eral means  devised  for  overcoming  this  and  making  the  pavemenjt 
more  elastic.  The  Asphalt  Wood  Paving  Co.  laid  -J  inch  of  asphalt 
upon  concrete,  and  formed  also  the  lower  part  of  the  joint  with 
the  same  material,  and  the  upper  part  with  a  grout  of  Portland 
cement  and  gravel.  In  addition  to  the  elasticity,  it  was  claimed 
that  this  also  gave  a  perfectly  water-tight  joint.  One  objection 
to  this  method,  however,  was  that  the  asphalt  softened  under 
blocks  when  the  weather  became  hot,  allowing  them  to  settle  un- 
evenly under  traffic,  making  the  pavement  generally  uneven  and 
consequently  causing  abnormal  wear. 

Still  another  system  was  what  was  known  as  Henson's.  In  this 
method  the  blocks  were  laid  close,  with  a  strip  of  roofing-felt  from 
1/16  to  1/8  of  an  inch  thick,  cut  to  the  same  width  as  the  depth  of 
the  blocks,  laid  between  each  course.  The  joint  was  thus  closed 
as  completely  as  possible,  leaving  only  the  actual  fabric  of  the 
felt,  the  material  support  of  the  blocks  saving  them  from  the 
rapidly  destroying  action  of  spreading  at  the  edges.  The  pro- 
tection of  the  wood  was  further  enhanced  by  a  layer  of  similar 
felt  over  the  whole  surface  of  the  concrete  foundation  upon  which 
the  wooden  blocks  were  cushioned.  Another  object  of  laying  the 
felt  between  the  blocks  was  to  take  up  any  longitudinal  expansion 
that  might  occur  on  account  of  the  changes  of  the  atmosphere. 
It  was  thought  that  the  felt  would  be  thick  enough  to  provide  for 
the  expansion  of  any  one  course  of  blocks.  The  results  justified 
this  method,  which  was  somewhat  expensive,  but  the  endurance 
of  the  blocks  was  said  to  be  increased  from  one-half  to  two-thirds 
by  this  freedom  from  the  joining  of  the  blocks-  and  the  mutual 
support  of  the  edges.  In  order  to  provide  for  the  transverse  ex- 
pansion a  space  of  1  or  1J  inches  was  left  along  by  the  curb  and 


296        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

fi]led  with  asphalt,  sand,  or  gravel.  In  some  cases,  however,  the- 
row  of  blocks  next  to  the  curb  was  left  open  until  the  greatest 
amount  of  expansion  had  taken  place,  and  then  filled  in. 

The  kind  of  wood  used  in  London  at  that  time  was  generally 
Swedish  deal,  and  the  blocks  were  generally  laid  without  any 
chemical  treatment,  as  that  was  considered  of  doubtful  ad- 
vantage, as  they  wore  out  under  traffic  rather  than  failed  from 
decay,  and  it  was  not  thought  that  creosoting  or  similar  treat- 
ment would  benefit  the  wearing  qualities. 

In  1874  Mr.  Wm.  Haywood  made  an  extensive  report  to  the 
Commissioners  of  Sewers  of  London  upon  the  comparative  merits, 
of  wood  and  asphalt  pavements.  At  that  time  there  were  but 
12,238  square  yards  of  wood  pavement  and  30,802  square  yards  of 
asphalt,  quite  a  portion  of  the  area  previously  laid  with  wood 
having  been  replaced  with  asphalt. 

In  a  table  which  he  presented  at  that  time  he  gave  the  actual 
life  of  wooden  pavements  that  had  been  laid  at  different  times, 
since  1841  as  varying  from  five  years  and  five  months  to  nineteen 
years  and  one  month.  The  pavement  having  the  longest  life, 
strangely  enough,  was  the  first  one  laid  of  those  in  the  table.  The 
average  cost  per  square  yard  during  life,  including  repairs,  varied 
from  Is.  5^d.  to  3s.  4d.,  which  last  pavement  had  a  life  of  twelve 
years  and  three  months.  He  gave  the  average  life  of  the  pave- 
ments in  the  three  streets  of  the  largest  traffic  as  nine  years,  and 
those  of  the  least  traffic  as  eleven  years  and  three  months.  His 
conclusions  on  the  whole  were  more  favorable  to  asphalt  than  to 
wood,  although  the  experience  with  asphalt  at  that  time  extended 
over  a  period  of  only  five  years,  but  later  experience  has  justified 
his  conclusions.  London  at  the  present  time  is  using  wood  as  a 
paving  material  practically  for  the  same  reasons  as  those  given  for 
Paris — because  it  is  less  noisy  than  stone  and  less  slippery  than 
asphalt. 

On  London  Bridge,  King  William  Street,  blocks  wore  2f  inches 
in  three  years  and  two  months,  the  traffic  being  12,000  vehicles  per 
yard  for  twelve  hours.  Mr.  Haywood  estimated  in  general  that 
the  wear  of  wooden  pavements  would  be  from  2/10  to  3/10  of  an 
inch  per  year,  under  traffic  of  from  300  to  660  vehicles  per  yard 
for  twelve  hours. 


WOOD  PAVEMENTS.  297 

In  1884  the  wood  pavements  in  London  consisted  generally  of 
blocks  3  inches  wide  by  6  inches  deep  by  9  inches  long,  although 
the  dimensions  of  length  and  depth  varied  somewhat. 

Swedish  deal  blocks  laid  on  concrete  with  a  cushion-coat  of 
asphalt  cost  $3.08  per  square  yard  and  had  an  average  life  of  seven 
years  and  cost  $0.209  annually  for  repairs.  Creosoted  blocks,  lime 
joints,  cost  $2.95  per  square  yard,  with  an  average  life  of  eight 
years,  and  cost  $0.204  per  year  for  repairs.  Creosoted  blocks  with 
asphalt  mastic  joints  cost  $3.55  per  yard,  with  an  average  life  of 
eight  years,  and  cost  $0.24  per  year  for  repairs.  Pitch-pine  blocks 
cost  $2.91  per  square  yard,  with  cement  joints,  with  a  life  of  eight 
or  nine  years,  and  were  maintained  at  an  expense  of  $0.088  per 
square  yard  per  year  for  repairs.  The  life  of  these  foreign  pave- 
ments is  estimated  for  the  traffic  standard  of  750  tons  per  yard  of 
width  per  day. 

The  cost  of  repairs  varies  very  much  with  the  method  of  mak- 
ing them.  A  contract  was  made  to  keep  Piccadilly  and  part  of 
Kings  Road  in  repair  for  fifteen  years  for  3s.  per  yard  per  year, 
when  the  engineer  estimated  that  its  cost  would  not  be  more  than 
2s.  The  annual  cost  per  square  yard  for  a  plain  deal,  spread  over 
fifteen  years,  ran  Is.  3|d.,  with  a  traffic  of  279  tons,  to  3s.  2d.  for 
improved  pitch-pine,  with  a  traffic  of  558  tons  per  yard  per  day. 
These  figures  were  made  in  1884.  In  1893  a  portion  of  the  Euston 
Eoad  was  paved  with  wood — 63  feet  with  yellow  deal,  62  with 
Karri,  49  with  yellow  deal,  and  63  with  Jarrah.  After  three  years' 
time  the  wear  was  found  to  be  J  inch  on  Jarrah  and  Karri,  and  If 
inches  on  the  deal.  From  observations  taken,  the  traffic  was  found 
to  be  575,544  tons  per  yard  of  width  per  anjium.  On  another  por- 
tion of  the  same  road  the  wear  was  £  inch  per  annum  with  a  traffic 
of  411,318  tons. 

Tottenham  Court  Road,  which  was  paved  with  Jarrah  blocks, 
showed  only  J  inch  of  wear  after  three  years,  with  greater  traffic 
than  Euston  Road,  and  on  the  Westminster  Bridge  Road  after 
nearly  seven  years  of  wear  the  Jarrah  blocks  had  worn  from  11/1Q 
to  1V8  inches,  with  a  traffic  of  from  233  to  334  tons  per  foot  of 
roadway  in  twelve  hours. 

Table  No.  70  gives  information  relative  to  hard-wood  pave- 
ments in  London. 


298        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

TABLE  No.  70. 


First  Cost 

...   . 

^ 

and  Cost  of 

a] 

Renewal. 

OS 

0) 

,      Parish 

Kind 

t* 

A« 

*"§ 

ii 

1    • 

or 

of 

"^•o 

S  a  oo 

^  *  0 

o 

3  * 

Remarks. 

District. 

Wood. 

•w  oj 

<-*  _.  o 

o     o 

*^3 

^^H 

IS 

III 

»ll 

^0 

a 

!! 

l|i 

ill 

II 

|l 

0.0} 

S9  £)pE| 

M   U  fe 

>  3 

>  E^ 

M 

K 

-Jj 

<j 

Fulham  

Jarrah 

542 
2202 

4  50 

Complaints  as  to  slipperiness. 

Holborn  

Islington  •< 

Jarrah, 
Karri, 
BlueGum 

!•  27000 

(2.83 
1   to 
(3,18 

[... 

"i 

Baltic  deal  not  entirely  super- 
seded. 

The  vestry  buys  material  and 

Lambeth  •< 

Jarrah, 
Karri, 
BlueGum 

VI  20000 

(  3.40 
1    to 
(3.50 

2.54 
to 
2.6<J 

1 

does  its  own  sawing,  with  ap- 
parently economical   results. 
The  surveyor  reports  favora- 

I 

i 

[ 

bly. 

Poplar  

-\ 

Insufficient  experience. 
Small  trial  strip  only.    Survey- 
or prefers  deal. 

St.      George,  j 
Hanover  Sq.  ( 

Karri 

St.        George  j 
the  Martyr.  .  } 

Jarrah 

j-  23000 

3.50 

1 

15to| 
20    f 

10  ] 

Hardwood  first  adopted  in  1893. 
Soft  wood  now  abandoned. 

St.  Martin-in-j 

Jarrah, 

i 

.  „           1 

tbe-Fields..."j 

Karri 

>     8450 



2.75 

l^TS 

l«>t 

St.  Pancras..  -j 

Jarrah, 
Karri, 
BlueGum 

i  110000 



(2.62 
-j    to 
(2.87 

[.... 

-i 

Hardwood  will  probably  be  ex- 
tensively used  in  this  parish. 

Wands  worth  < 

Jarrah, 
Karri, 

-rrt  _„_  V» 

j-  18000 

4.12 

9 

7I 

It  is  not  proposed  to  increase 
the  use  of  hardwood  to  any 
great  extent. 

Kensington  .  .  -j 

Jarran, 
Karri 

j-     3509 

Not  satisfactory. 

Hardwood  paving  has  not  been  sufficiently  long  in  use  to  judge  accurately  as  to  its  life 
under  varying  conditions,  but  generally  it  would  appear  to  last  about  twelve  years.  The 
Council  in  granting  loans  of  this  kind  allows  a  period  of  ten  years  for  the  repayment 
thereof.  For  heavy  traffic  the  material  is  likely  to  be  extensively  used,  although  in  several 
districts  Baltic  deal  is  still  employed  in  preference,  the  average  cost  of  the  latter  being 
$1.68  per  square  yard,  and  the  life  from  five  to  eight  years. 

NOTE. — The  above  information  concerning  hardwood  pavements  in  London  was  fur- 
nished the  author  by  the  Clerk  of  the  Councif  in  1899. 

London  Specifications. 

Hard-wood  Pavements. — The  surface  is  to  be  laid  to  such,  curva- 
tures, currents,  and  inclinations  as  may  be  needful  to  enable  the 
water  to  run  off  with,  the  best  selected  Karri  or  Jarrah  blocks 
3"  x  9"  x  5"  deep,  sawn  true  and  free  from  shakes  and  gum-holes 
and  thoroughly  seasoned.  The  blocks  are  to  be  laid  close  with  the 
grain,  vertical,  in  transverse  rows  at  right  angles  with  the  channel- 


'  WOOD  PAVEMENTS.  299 

courses;  the  channel  to  be  formed  of  three  rows  of  blocks  laid 
parallel  with  curbs.  These  channel-courses  are  to  be  dipped  in  a 
mixture  of  boiling  tar  and  pitch  in  the  proportion  of  four  to  one, 
and  laid  close  and  well  in  advance  of  the  general  work,  an  expan- 
sion-joint one  inch  wide  to  be  left  next  to  the  curbs  and  to  be  filled 
in  with  sand.  A  mixture  of  boiling  tar  and  pitch  mixed  in  the 
proportion  of  five  to  one  is  to  be  poured  over  the  entire  surface 
of  the  wood  pavement  and  worked  into  the  interstices  between  the 
blocks  and  cleaned  over  with  squeegees;  the  surface  is  then  to 
be  floated  with  cement  grout  brushed  over  same  until  every  in- 
terstice is  perfectly  filled  up,  and  a  coating  of  clean,  sharp  Thames 
sand  to  be  immediately  thereafter  spread  over  the  surface. 

Soft-wood  Pavements. — No  tender  for  blocks  less  than  six  inches 
in  depth  will  be  accepted.  The  blocks  are  to  be  of  the  best  yel- 
low deal  and  are  to  be  creosoted; — the  creosoting  used  is  to  be  of 
the  best  creosote  oil  free  from  adulteration  and  heated  to  a  tem- 
perature of  220°  Fahr.,  and  forced  into  the  blocks  under  a  pres- 
sure of  144  Ibs.  to  the  square  inch,  the  steam  generated  being  first 
withdrawn  from  the  creosoting-cylinder  by  means  of  an  air-pump. 
The  creosote  as  described  is  to  be  forced  into  the  blocks  as 
specified  to  the  amount  of  12  Ibs.  to  the  cubic  foot  of  timber, 
which  must  be  ascertained  by  weighing  the  wood  before  putting  it 
into  the  cylinder  and  weighing  it  after  it  has  been  taken  out.  The 
blocks  are  to  be  laid  on  the  concrete  foundation  with,  grain  ver- 
tical, in  transverse  rows  at  right  angles  with  the  channel-courses, 
the  joints  to  be  close.  The  channels  are  to  be  formed  with  three 
courses  of  blocks  laid  parallel  with  the  curbs, — an  expansion-joint 
at  least  one  inch  wide  being  left  next  the  curbs.  The  joints  of 
the  pavement  are  to  be  grouted  and  filled  up  solid  with  a  mixture 
of  blue  lias  lime  and  sand,  and  the  surface  to  be  dressed  with  a 
layer  of  fine  hoggin  or  gravel. 

» 

The  Surveyor  for  the  Board  of  Works  for  the  Strand  District, 
London,  says  (Feb.,  1900): 

"  The  system  of  laying  wood  pavements  during  the  past  twenty 
years  has  little  altered,  and  the  best  pavement  is  considered  to  be 
the  soft  wood  [Baltic  timber]  creosoted  and  laid  with  small  jo'nts 
run  in  with  bitumen  and  grouted  with  Portland  cement  and  sand,. 


300        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

the  whole  laid  on  a  Portland-cement  concrete  substratum.  This 
pavement  has  given  excellent  results  on  steep  hills  with  heavy 
traffic,  where  granite  setts  were  found  very  trying  to  the  horses; 
the  wood,  however,  has  to  be  kept  very  clean  to  give  good  foot- 
hold." 

The  average  cost  of  maintaining  114,215  square  yards  in  the 
parishes  of  St.  Margaret  and  St.  John  for  the  year  ending  March 
25,  1899,  was  5.2  cents  per  square  yard. 

The  Surveyor  to  the  Works  Committee  of  Paddington  says  in 
a  report  dated  November  4,  1899: 

"  As  the  traffic  now  is  so  enormous,  I  am  of  the  opinion  that 
very  little  advantage  is  gained  by  having  deal  blocks  creosoted, 
certainly  not  to  warrant  the  entire  expense;  they  are,  perhaps, 
more  sanitary  the  first  two  years,  and  prevent  a  certain  amount 
of  soaking  into  them,  but  you  do  not  in  any  way  add  to  the  life  of 
the  wood,  for  it  is  perfectly  plain  that  all  descriptions  of  wood 
paving  after  four  or  five  years'  wear  become  wavy  and  rough;  then 
numerous  complaints  are  made  that  the  roadway  is  bad  and  worn 
out,  when  such  is  not  the  fact,  there  still  being  three  to  four 
inches  in  depth  of  good  wood/7 

In  a  paper  read  before  the  Association  of  Municipal  and 
County  Engineers  of  Great  Britain  in  the  summer  of  1899,  Mr. 
Edward  Buckham,  Borough  Engineer  of  Ipswich,  gave  a  descrip- 
tion of  the  wood  pavements  laid  in  that  city,  which  is  a  good  sam- 
ple of  the  way  such  pavements  are  laid  in  England  at  the  present 
time. 

The  blocks  used  in  the  first  pavements  were  of  fir,  5  inches 
deep,  and  laid  on  a  base  of  6  inches  of  lime  concrete.  Later,  how- 
ever, the  depth  of  the  blocks  was  reduced  to  4J  inches,  which  is  the 
present  standard. 

An  experimental  length  of  pavement  was  laid  on  a  1-inch  bed 
of  gravel  without  any  concrete.  The  advocates  of  this  plan  urged 
that  the  gravel  base  would  afford  a  better  drainage  than  the  con- 
crete and  that  consequently  the  blocks  would  last  much  longer. 
Experience,  however,  showed  just  the  reverse,  as  the  moisture, 
instead  of  soaking  away,  worked  up  through  the  gravel  and  the 
lower  pottion  of  the  blocks  decayed.  Consequently  concrete  was 
adopted  as  a  base  for  all  wood  pavements.  In  the  place  of  the 


WOOD  PAVEMENTS.  301 

"6-inch  lime  base,  however,  a  bed  of  Portland-cement  concrete  3 
Inches  thick  was  used.  The  concrete  was  mixed  in  the  proportion 
of  one  part  of  Portland  cement  to  one  part  of  sand  and  four  parts 
of  gravel.  Upon  the  concrete  was  spread  a  half-inch  coat  of 
-cement  mortar,  mixed  with  one  part  of  Portland  cement  and  three 
parts  of  sand.  Upon  this  the  blocks  are  laid,  with  ^-inch  joints, 
regulated  with  a  lath  between  them.  The  laths  are  afterwards 
taken  out'and  the  joints  filled  with  a  grout  composed  of  one  part 
of  Portland  cement  and  two  parts  of  sand.  This  is  swept  into  the 
joints  until  they  are  entirely  filled.  After  the  cement  of  the  joints 
is  set,  fine  gravel  and  coarse  sand  are  sprinkled  over  the  surface, 
and  the  travel  allowed  to  come  upon  it.  The  particles  of  stone 
are  crowded  into  the  surface  of  the  blocks  by  the  action  of  traffic, 
and  the  surface  is  made  much  harder  in  consequence.  The  early 
pavements  were  laid  with  plain  wood,  but  when  they  came  to  be 
renewed  creosoted  blocks  were  used.  The  life  of  these  pavements 
has  been  from  eight  to  ten  years  for  plain  wood,  while  the  only 
•street  paved  with  the  creosoted  blocks  for  any  length  of  time  has 
l>een  down  thirteen  years  and  will  probably  last  fifteen. 

It  is  estimated  that  creosoting  adds  50  per  cent  to  the  life  of  a 
pavement. 

Wood  pavement  was  first  laid  in  Glasgow  in  1841.  Beech  tim- 
ber was  used,  but  instead  of  being  sawed  into  square  logs,  round 
timber  was  cut  into  short  lengths  and  placed  on  end.  The  wood 
soon  decayed,  however,  and  had  to  be  removed.  Wood  paving  was 
again  tried  in  1874,  when  a  portion  of  one  street  was  paved  with 
yellow-pine  blocks.  The  blocks  were  laid  on  a  foundation  of  plank 
and  sand,  the  joints  being  filled  with  cement.  This  pavement  lasted 
only  until  1877,  when  it  was  repaved  by  the  same  company.  In 
1881  it  again  required  extensive  repairs,  and  in  1885  the  entire 
pavement  was  removed  and  a  new  system  of  laying  blocks  adopted. 
This  pavement  was  laid  on  a  Portland-cement  concrete  base,  and 
the  joints  were  filled  with  bitumen.  Side  streets  have  since  been 
paved  in  this  manner,  and  Australian  wood  has  been  used  to  a  cer- 
tain extent,  but  stone  has  always  remained  the  principal  paving 
material. 

In  his  report  dated  October  30,  1897,  the  Master  of  Works  in 
Glasgow  says:  "In  regard  to  the  durability  of  timber  as  a  pav- 


302        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

ing  material,  the  soft  varieties,  in  my  opinion,,  are  not  at  all  suited 
for  our  city.  For  the  first  two  years  they  wear  well  enough,  but 
after  that  time  give  way  rapidly.  No  doubt  carbolizing  has  a  fav- 
orable effect  in  preserving  to  some  extent  from  the  effect  of  mois- 
ture. So  far  as  regards  the  durability  of  the  hard  timbers,  it 
cannot  yet  be  stated  how  age  will  affect  them,  but,  so  far  as  can  be 
judged  from  the  blocks  put  down  in  Buchanan  Street,  J;he  extent 
of  the  wear  of  the  material  since  laid  down  seems  to  be  compara- 
tively light,  while  the  substance  or  fibre  of  the  wood  does  not  show 
any  appearance  of  being  shattered  as  it  does  in  the  soft  varieties." 

About  1872  wood  pavements  were  laid  in  Edinburgh  with  Bal- 
tic redwood  blocks,  but  they  did  not  give  satisfaction  and  were 
taken  up  after  eight  or  ten  years  and  replaced  with  stone.  The 
blocks  were  practically  of  the  same  dimensions,  and  laid  in  the 
same  manner  as  those  of  London. 

Dublin,  Ireland,  also  has  some  wood  pavements.  The  blocks 
are  of  beech  or  pine,  3  inches  wide,  5  inches  deep,  and  9  inches 
long.  These  blocks  are  generally  creosoted  before  laying,  10  Ibs. 
of  creosote  being  used  on  an  average  for  one  cubic  foot  of  wood. 
The  foundation  consists  of  6  inches  of  cement  concrete,  and  the 
joints  are  partially  filled  with  hot  pitch  and  creosote  oil,  when  the 
remaining  space  is  filled  with  a  mixture  of  one  part  of  cement  and 
six  parts  of  gravel,  partly  to  solidify  the  pavement  and  partly  to 
protect  the  pitch  and  creosote  from  the  action  of  the  sun.  This 
pavement  is  said  to  have  an  average  life  of  ten  years. 

Wood  pavements  were  also  laid  about  the  same  time  in  Berlin, 
some  of  American  cypress,  and  others  of  Swedish  pine.  It  is  said 
that  in  1883  a  pavement  laid  in  1879  in  Oberwall  Street  had  be- 
come so  much  damaged  that  half  of  it  had  to  be  relaid,  and  the 
other  half  the  following  year.  In  another  street  a  pavement  laid 
in  1879  was  replaced  by  asphalt  in  1884. 

In  1891  Consul-General  Edwards  translated  from  the  Berlin 
Journal  as  follows:  "  It  is  reported  that  the  wood  pavement  which 
was  laid  in  many  parts  of  Berlin  has  worn  so  badly  that  the  Munici- 
pal Street  Commission  has  decided  to  entirely  stop  using  this 
material  for  paving  purposes.  Every  sort  of  wood  which  has  yet 
been  tried  has  rotted  in  a  comparatively  short  time,  and  its  upper 
surface  has  become  so  much  injured  that  repairs  are  hardly^  pos- 


WOOD   PAVEMENTS.  303 

sible;  also  horses  fall  upon  it  more  easily  than  upon  asphalt  pave- 
ment." 

Paris  did  not  adopt  wood  as  a  paving  material  until  after  the 
earlier  improvements  in  London,  and  not  until  it  had  been  de- 
monstrated about  what  the  pavement  was  capable  of.  It  was  used, 
not  as  a  cheap  or  durable  material,  but  as  one  that  would  give 
results  that  would  be  much  less  noisy  than  stone  and  much  less 
slippery  than  asphalt.  The  decaying  properties  of  the  material 
were  not  seriously  considered,  because  it  was  expected,  as  proved 
to  be  the  case,  that  the  pavement  would  be  worn  out  by  the 
severe  traffic  of  the  streets  before  any  action  of  decay  would 
set  in.  The  blocks  are  about  3^  inches  wide  by  4J  inches  high 
and  6  inches  long,  and  are  set  directly  upon  the  foundation, 
the  surface  of  which  is  made  perfectly  smooth  to  receive  them. 
The  blocks  are  set  in  courses  at  right  angles  to  the  street,  with  a 
space  of  7/16  of  an  inch  between  them.  Some  pavements  have 
been  laid  with  J-  and  J-inch  joints,  but  this  is  not  the  custom. 
The  blocks  are  kept  the  proper  distance  apart  by  strips  of  wood 
1£  to  2  inches  broad  and  about  5  feet  long,  which  are  laid  obliquely 
between  rows,  with  the  ends  projecting  above  the  surface,  so  that 
they  can  be  readily  withdrawn  when  half  a  dozen  or  more  rows 
have  been  laid.  As  soon  as  they  are  taken  out,  hot  coal-tar  is 
poured  into  the  joints,  so  as  to  fill  them  to  a  depth  of  about  1  inch. 
The  remaining  space  is  filled  with  a  grout  made  of  Portland 
cement  and  sand.  The  surface  of  the  pavement  is  covered  with  a 
thin  layer  of  clean,  sharp  gravel,  so  that  it  may  be  ground  into  the 
surface  of  the  block  by  traffic,  making  them  harder  and  more 
durable.  To  provide  for  expansion  a  joint  is  left  next  to  the  curb 
about  2  inches  wide,  which  is  filled  with  sand. 

Norway  spruce  and  fir  were  used  at  first,  but  later  pine  from 
the  southern  part  of  France  and  some  pitch-pine  from  Florida 
have  given  better  results.  Still  later  experiments  have  been  made 
with  the  Australian  woods,  which  will  be  taken  up  later  on.  The 
average  life  of  the  pavements  has  been  from  eight  to  nine  years 
upon  heavy-traffic  streets.  The  blocks  in  some  instances  have  been 
worn  down  to  half  of  their  original  depth.  The  wear  on  some  ten 
of  the  principal  streets  has  varied  from  .0746  to  .2908  of  an  inch 
per  year.  The  average  cost  of  wood  pavements  in  Paris  has  been 


304        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

about  $3.47  per  square  metre,  and  the  cost  of  maintenance  29 
cents  per  square  metre  per  year.  In  January,  1897,  Paris  had 
1,339,520  square  yards  of  wood  pavements. 

In  1890  the  city  of  Montreal  laid  a  pavement  of  tamarack 
blocks  made  from  3-inch  planks  of  the  following  dimensions:  3 
inches  thick,  5  inches  wide,  and  6  inches  deep.  The  blocks  were 
creosoted  and  then  laid  closely  together  on  concrete,  and  a  coating 
of  hot  coal-tar  and  pitch  poured  over  the  entire  surface  until  the 
blocks  and  joints  would  absorb  no  more,  when  the  entire  pave- 
ment was  covered  with  fine  roofing-gravel  about  1  inch  in  thick- 
ness. 

Tamarack  blocks  have  also  been  laid  in  Quebec,  being  first  used 
there  in  1855.  The  following  description  of  the  pavement  is  taken 
from  a  consular  report: 

"  The  street  is  excavated  to  a  depth  of  2  feet,  properly  graded, 
and  rolled  with  a  horse-roller.  Then  a  foundation  is  made  of 
wooden  flooring  of  IJ-inch  boards  laid  longitudinally  and  crossed 
at  right  angles  by  a  second  flooring  of  inch  boards  so  as  to  con- 
form more  readily  to  the  crown  of  the  roadway.  These  are  laid 
with  J-  or  f-inch  spaces  between  so  that  should  any  surface-water 
penetrate  it  will  not  remain  and  freeze,  but  run  through  and  be 
absorbed  by  subsoil,  after  passing  through  a  layer  of  sand  which 
is  strewn  over  the  flooring  to  the  depth  of  \  inch,  thus  prevent- 
ing the  blocks  coming  in  contact  with  the  flooring.  This  double 
flooring  is  the  means  of  distributing  the  weight  of  passing  loads 
over  the  extent  of  area,  and  also  prevents  any  local  settlement  of 
the  surface.  On  the  flooring  are  laid  blocks  of  red  tamarack  about 
12  inches  long,  as  sawn  from  the  log,  about  10  or  15  inches  in 
size,  and  placed  on  end.  In  the  spaces  formed  around  the 
blocks  small  pieces  of  wood  are  forced,  thus  filling  in  and  tighten- 
ing the  mass.  The  interspaces  remaining  are  then  filled  with  a 
grout  made  of  sand,  cement,  and  tar,  or  a  mixture  of  finely-sifted 
coal-ashes  and  cement.  The  surface  is  evenly  rolled  and  covered 
with  sand,  which  is  allowed  to  remain  until  every  cavity  is  filled, 
when  the  street  is  swept  clean  on  the  block. 

"  These  roads  are  very  durable.  Pavements  laid  thirty-five 
years  ago  were  recently  taken  up  and  the  tamarack  blocks  had  not 
shown  any  signs  of  decay,  but  had  worn  down  to  about  half  their 


WOOD  PAVEMENTS.  305 

original  length.  The  surface  was  as  hard  as  stone,  and  it  is  said 
that  there  is  more  resistance  to  these  surfaces  practically  than 
stone,  because  stone,  under  the  influence  of  water  and  constant 
teaming,  wears  away  like  a  grindstone.  The  vertical  pores  of  the 
wooden  blocks  fill  with  grit,  and  the  fibres  of  the  wood,  like  the 
bristles  of  a  brush,  sway  to  and  fro  with  the  traffic  of  opposite 
directions  without  breaking.  The  blocks  are  used  in  their  green 
state,  with  bark  on,  which  prevents  the  wood  from  coming  in  con- 
tact with  the  filling,  and  the  bark  lasts  for  many  years,  as  precau- 
tion is  taken  to  cut  down  the  trees  in  the  proper  season  after  the 
sap  has  all  been  reduced  to  fibre  and  before  the  spring  sap  begins 
its  ascension  through  the  pores  of  the  wood.  The  cost  of  this 
pavement  is  from  $1.50  to  $1.75  per  square  yard.  In  the  older 
part  of  the  city  a  number  of  the  streets  are  planked  with  3-inch 
pine  deals.  These  streets  are  very  narrow,  the  entire  width  being 
only  from  8  to  12  feet." 

Any  extended  writing  about  the  wooden  pavements  of  the 
United  States  must  of  necessity  be  principally  history.  While 
during  the  last  thirty  years  many  millions  of  yards  of  wood  pave- 
ments have  been  laid,  at  the  present  time  very  few  cities  are  lay- 
ing them  to  any  extent. 

Just  when  wood  was  adopted  as  a  paving  material  in  this  coun- 
try is  uncertain.  In  a  report  of  the  Committee  on  Paving  Mate- 
rials to  the  Franklin  Institute,  made  in  September,  1843,  and 
referred  to  in  the  chapter  on  Stone  Pavements,  extended  mention 
was  made  of  the  wood  pavements  of  Philadelphia.  The  following 
quotations  from  that  report  will  give  the  standing  of  wood  pave- 
ments at  that  time: 

"  The  hexagonal  hemlock  pavement  laid  some  years  ago  in 
Chestnut  Street,  between  Fourth  and  Fifth,  cost  $2.50  per  square 
yard,  and  was  decayed  to  such  an  extent  as  to  require  renewal 
within  three  years." 

"  The  squared-block  wooden  pavement  in  Third  Street,  of 
Northern  spruce,  cost  about  $2.25  per  square  yard,  and  after  three 
and  one-half  years'  use  the  hemlock  portion  of  it  is  very  much 
decayed  and  needs  renewal,  while  the  heart  yellow-pine  portion  is 
still  in  apparently  good  order,  although  presenting  strong  symp- 
toms of  decay.  This  pavement  was  laid  in  September,  1839,  and 


306        STREET  PAVEMENTS    AND  PAVING  MATERIALS. 

the  hemlock  will  probably  require  removal  in  the  course  of  the 
present  year  [1843]." 

"  The  wooden  pavement  of  white  cedar  formed  of  oblique 
prisms,  dowelled  together  on  the  Count  de  Lisle's  plan,  which  was 
laid  in  Walnut  Street  in  1840,  cost  $1.75  per  square  yard  and  is. 
still  in  good  order." 

"  The  cubical  hemlock  pavement  in  front  of  the  State  House> 
laid  in  July,  1839,  has  so  extensively  decayed  that  it  has  this  year 
been  replaced  by  a  cubical  pavement  of  stone  laid  upon  the 
diagonal  plan." 

"  The  squared  hemlock-block  pavement  laid  in  Spruce  Street 
cost  about  $2  per  square  yard  in  November,  1839,  and  although 
exposed  to  very  little  travel,  it  now  exhibits  unequivocal  symptoms. 
of  speedy  destruction.  The  hemlock  which  has  been  chiefly  used 
in  Philadelphia  for  wooden  paving  is  certainly  the  most  unsuitable 
timber  that  could  have  been  employed  for  such  purpose.  Never- 
theless its  very  rapid  decay  showed  but  too  clearly  the  great  lia- 
bility of  wood  in  general  to  rot  under  such  circumstances." 

The  Gommittee  instanced  one  example  of  a  wooden  pavement 
laid  with  chemically-treated  blocks,  which  they  stated  were  much 
decayed  at  that  time,  but  did  not  give  the  date  of  laying.  They 
add,  however,  that  it  was  stated  that  the  blocks  were  somewhat 
rotten  prior  to  being  boiled  in  the  solution  of  the  sulphates  of 
copper  and  iron.  They  conclude  their  deductions  as  follows: 

"  Finally,  in  consequence  of  the  slippery  nature  of  their  sur- 
face, their  deficiency  of  durability  when  of  ordinary  timber,  of 
their  expense  in  the  ultimate,  and  in  view  of  results  of  experience 
as  far  as  they  have  become  known  to  us,  we  are  reluctantly  im- 
pelled to  the  conclusion  that,  though  their  use  may  be  proper  in 
some  detached  situations,  wooden  pavements  ought  not  at  this 
time  to  be  recommended  as  part  of  the  general  system  of  paving 
by  the  city  of  Philadelphia." 

They  also  added  that  since  the  report  was  written  they  had 
learned  that  the  authorities  of  New  York  had  determined  to  take 
up  their  decayed  wooden  pavements  and  relay  them  with  stone; 
also  that  they  had  learned  with  regret  that  the  experience  of  Bos- 
ton had  been  practically  the  same  as  that  of  Philadelphia  and  New 
York. 


WOOD  PAVEMENTS.  307 

While  only  history,  the  above  is  interesting  and  important,  as 
it  shows  the  conclusion  arrived  at  at  that  time  to  be  practically 
the  same,  as  relates  to  this  particular  material,  as  would  be  found 
by  a  committee  of  engineers  appointed  for  the  same  purpose  at 
the  present  time;  and  if  this  conclusion  had  been  accepted  by  the 
cities  of  the  country  as  a  whole,  a  large  amount  of  money  would 
have  been  saved  that  has  been  wasted  in  experimenting  with  wood 
pavements. 

Probably  no  city  in  the  country  has  had  as  great  a  variety  of 
pavements  laid  with  this  material  as  the  city  of  Washington. 
When  the  Board  of  Public  Works  of  that  city  was  appointed  in 
1871,  the  pavement  question  was  far  from  settled,  and  a  great 
many  experimenters  were  in  the  field.  Previous  to  this  date  there 
had  been  a  little  over  100,000  square  yards  of  wood  pavement  laid 
in  Washington  and  Georgetown.  Just  what  kind  this  was  is  not 
known,  but  probably  quite  a  proportion  of  it  was  the  Nicholson,  as 
that  was  laid  in  many  cities  previous  to  1870. 

Subsequent  to  1871,  and  under  the  authority  of  the  Board  of 
Public  Works  of  the  first  Board  of  Commissioners,  there  were  laid 
in  Washington  1,087,738  square  yards  of  wood  pavements,  under 
twelve  separate  patents.  These  had  cost  from  $2  to  $4.20  per 
square  yard.  They  soon  began  to  decay,  and  after  two  or  three 
years  began  to  be  replaced,  and  between  1875  and  1878  over 
315,000  square  yards  had  been  removed.  From  this  time  on  they 
were  gradually  replaced  by  other  material,  until  in  1887  about 
18,403  yards  were  left,  and  the  last  was  removed  in  1889.  In  a  re- 
port to  the  Engineering  Department  in  1887,  the  Commissioner 
says,  when  speaking  on  this  subject:  "  Cedar-block  pavements 
Tised  so  extensively  throughout  the  Northwest  are  cheap — $1  to 
$1.30  per  square  yard — but  deteriorate  rapidly,  are  objectionable 
on  sanitary  grounds,  and  are  anything  but  smooth  for  street  wear. 
Creosoted  wooden  blocks,  with  a  hydraulic-cement  foundation, 
when  closely  laid,  approach  nearest  to  the  ideal  block  pavement. 
Those  in  the  form  of  the  blocks  of  the  Ker  Pavement  Co.,  New 
York,  are  a  fair  example  of  this  class.  These  are  laid  with  creo- 
soted  wooden  blocks,  6x9x3  inches  in  dimension.  The  wood 
iibre  is  placed  vertically  to  a  depth  of  6  inches;  f-inch  joints  are 
left  which  are  filled,  1  inch  with  hot  asphalt  and  3  inches  with 


308        STREET  PAVEMENTS  AND  PA  VINO  MATERIALS. 

Portland-cement  grouting.  The  resulting  pavement  is  clean,, 
noiseless,  smooth,  and  not  slippery." 

Very  little  information  can  be  obtained  concerning  the  early 
wood  pavements  of  New  York  and  Boston,  but  they  were  in  use- 
in  both  cities  previous  to  1839,  and  the  statements  of  the  Com- 
mittee of  the  Franklin  Institute  no  doubt  expressed  the  conditions 
fairly. 

St.  Louis  also  had  some  experience  with  pine  and  cottonwood 
pavements,  some  laid  plain  and  others  treated  chemically,  but 
with  the  same  results  as  the  other  cities  mentioned. 

Between  1860  and  1870  a  large  amount  of  wooden  pavement 
was  laid  in  many  cities  in  this  country  under  the  Nicholson  patent. 
The  best  description  of  this  pavement  can  probably  be  obtained 
by  quoting  from  the  Brooklyn  specifications  in  a  contract  made 
in  1869: 

"  The  wooden  blocks  of  the  Nicholson  pavement  are  to  be  of 
sound  white  pine  or  Southern  yellow  pine,  sawed  so  as  to  be  3 
inches  thick  and  6  inches  long;  the  blocks  for  paving  the  kennel 
to  be  sawed  to  a  uniform  level  so  that  a  channel-way  for  surface- 
water  will  be  formed  outside  the  curb-lines.  The  flooring  for 
blocks,  and  the  pickets  to  be  used  between  each  traverse  course 
of  blocks,  to  be  of  sound  common  pine  boards,  conforming  to  1 
inch  thickness,  the  whole  2  inches  wide  and  1  inch  thick.  The 
foundation  or  sand  bed  which  is  prepared  is  to  be  brought  to  a 
proper  crown  and  width  to  the  street  edge  and  then  covered  with 
sound  common  pine  boards  of  the  dimension  described,  paved 
lengthwise  to  the  line  of  the  street,  the  ends  resting  on  similar 
boards  laid  transversely  from  curb  to  curb;  the  flooring  to  be  well 
and  thoroughly  tarred  on  both  sides  with  hot  coal-tar  brought  to 
the  proper  consistency  with  paving-cement,  so  as  to  be  tough  and 
fibrous  and  not  brittle  when  cool.  Upon  this  floor  of  plank  the 
blocks  are  to  be  set  on  end  in  parallel  courses,  transversely  with 
the  line  of  the  street;  each  block  before  laying  to  be  dipped  to 
half  its  height  in  hot  coal-tar  and  paving-cement  prepared  as  de- 
scribed; each  course  to  be  separated  by  a  course  of  pickets  placed 
on  the  face  of  the  blocks  and  to  be  properly  nailed;  the  space  be- 
tween each  course  of  blocks  about  the  pickets  to  be  filled  with 
clean  roofing-gravel  and  hot  coal-tar,  and  then  the  cement  thor- 


WOOD  PAVEMENTS.  309 

oughly  mixed  and  compactly  rammed  by  means  of  a  paver's  ram- 
mer and  an  iron  blade  made  to  fit  the  interstices  or  spaces  be- 
tween the  blocks;  the  gravel  to  be  very  thoroughly  dry  and  warm,, 
so  as  not  to  chill  the  tar;  the  coal-tar  in  all  cases  is  to  be  boiled 
down  and  so  thickened  with  paving-cement  <as  to  be  tough  and 
fibrous  when  cool  and  not  brittle  even  in  cool  weather,  and  is. 
to  be  applied  hot  and  in  such  quantity  as  will  thoroughly  pene- 
trate and  fill  all  the  joints;  the  whole  surface  of  the  pavement,  as 
rapidly  as  the  grouting  shall  be  completed,  is  to  be  covered  with 
hot  tar  and  paving-cement  as  above  specified,  and  then  covered 
with  fine  sand  and  gravel  and  not  less  than  J  of  an  inch  thick." 

This  pavement  in  Brooklyn  cost  $4.50  per  square  yard,  with  an 
additional  sum  of  50  cents  for  grading  the  street  and  preparing 
the  foundation.  The  blocks  for  this  pavement  could  be  either 
treated  chemically  or  not,  according  to  the  belief  of  the  special 
set  of  authorities  in  control.  This  pavement  when  first  laid  was 
very  smooth  and  presented  a  pleasing  appearance  to  the  eye,  and 
for  the  time  was  extremely  popular,  but  it  soon  began  to  decay,, 
and  unless  frequently  repaired  was  rough  and  uneven,  and  as  the 
decay  continued  became  unhealthy  and  unsanitary.  Its  average 
life  in  Brooklyn  was  about  six  years,  and  in  St.  Louis  five  years, 
and  six  months. 

Memphis,  Tenn.,  laid  a  large  quantity  of  this  pavement,  whichA 
however,  soon  decayed,  requiring  relaying,  when  entirely  different 
material  was  used. 

Another  pavement  very  similar  to  the  Nicholson,  and  laid 
about  the  same  time,  was  what  is  known  as  the  Alexander  Miller 
&  Co.'s  Improved  Wood  Pavement.  The  principal  difference  be- 
tween this  and  the  Nicholson  was  in  the  shape  of  the  blocks,  which 
were  sawed  on  a  bevel  so  as  to  be  4  inches  thick  at  the  base,  3- 
inches  thick  at  the  top,  and  6  inches  deep,  so  that  when  set  to- 
gether at  the  bottom  they  left  an  open  joint  1  inch  wide  at  the 
top.  In  Brooklyn  these  blocks  were  laid  on  Burnettized  spruce 
planks  1J  inches  thick.  These  planks  were  laid  lengthwise  to  the 
street,  resting  on  similar  planks  laid  transversely  from  curb  to 
curb.  The  spaces  between  the  blocks  were  filled  with  coal-tar  and 
pitch,  and  the  surface  of  the  pavement  covered  in  the  same  way  as 
that  prescribed  for  the  Nicholson  pavement.  This  pavement  cost 


310        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

in  Brooklyn  $4.90  per  square  yard,  and  its  life  was  practically  the 
same  as  that  of  the  Nicholson, 

After  the  failure  of  these  pavements,  and  when  many  of  the 
Western  States  which  were  far  from  supplies  of  stone  had  at- 
tained such  size  and  importance  that  street  pavements  became  a 
necessity,  wood  was  laid  in  an  entirely  new  way.  Chicago  and 
Detroit,  wishing  a  new  and  cheap  pavement,  and  being  so  sit- 
uated that  they  were  in  close  connection  with  the  cedar-swamps  of 
the  North  by  means  of  water  communication,  finally  took  up  in 
earnest  what  is  the  well-known  cedar-block  pavement  of  the  West. 

These  blocks  were  made  of  cedar  posts,  from  which  all  the 
bark  had  first  been  removed,  sawed  into  pieces  6  inches  long,  by 
gang-saws  cutting  from  six  to  eight  blocks  at  once.  These  blocks 
varied  in  diameter  according  to  the  dimensions  of  the  posts,  but 
the  specifications  generally  called  for  them  to  be  from  4  to  8 
inches  in  diameter,  or,  if  larger,  the  blocks  were  to  be  split  before 
being  laid  in  the  pavement.  The  blocks  were  laid  on  different 
foundations,  some  simply  on  beds  of  sand,  some  upon  a  base  of 
sand  and  gravel,  some  on  sand  and  broken  stone,  some  on  sand  and 
hemlock  boards,  and  others  on  a  concrete  base  with  a  sand  cush- 
ion. The  great  and  almost  only  merit  of  these  pavements  was 
their  cheapness.  They  were  quickly  laid  and,  when  new,  made  a 
pleasing  and  apparently  satisfactory  roadway. 

There  was  considerable  discussion  as  to  the  best  foundation. 
A  sand  base  could  not  give  satisfaction,  as  it  was  easily  displaced 
and  the  surface  became  rough  and  uneven  before  the  blocks  began 
to  decay.  The  blocks  laid  on  hemlock  planks  maintained  their 
surface  as  long  as  the  blocks  and  the  planks  remained  sound,  but 
when  either  or  both  began  to  decay,  they  soon  became  rough  and 
in  a  short  time  almost  impassable. 

The  advocates  of  this  foundation  held  that  the  block  pavement 
was  cheap  and  only  temporary  at  best,  that  the  hemlock  founda- 
tion would  last  as  long  as  the  blocks,  and  that  when  the  pavement 
was  renewed  it  might  as  well  be  replaced  complete.  The  advocates 
of  the  broken-stone  and  concrete  bases,  however,  maintained  that 
if  a  permanent  base  were  laid  at  the  same  time  as  the  pavement, 
when  the  blocks  did  decay  and  required  replacing,  a  good  founda- 
tion would  be  in  position  for  whatever  material  should  be  selected, 


f 

WOOD  PAVEMENTS.  311 

whether  brick,  stone,  or  asphalt.  The  opponents  of  this  theory 
argued  that  a  concrete  foundation  held  the  moisture  which  would 
drain  off  through  the  stone  or  sand,  and  would  cause  the  blocks  to 
•decay  more  rapidly  than  otherwise.  This,  however,  was  not  borne 
out  by  experience,  as  the  life  of  the  pavements,  whether  laid  on 
sand  or  on  concrete,  did  not  vary  materially. 

The  blocks  were  laid  on  a  prepared  foundation  very  simply, 
the  only  object  being  to  get  them  laid  closely  so  as  to  form  as  small 
a  space  as  possible  between  each  individual  piece.  The  blocks 
were  rammed  and  the  space  filled  with  clean,  coarse  gravel  pre- 
viously heated  and  dried,  and  then  poured  full  of  paving-cement, 
the  specifications  generally  requiring  two  gallons  per  square  yard. 
Between  1880  and  1890  many  millions  of  yards  of  this  pavement 
were  laid  in  the  cities  of  Chicago,  Detroit,  St.  Paul,  Minneapolis, 
Omaha,  and  Kansas  City,  and  many  other  smaller  cities  through- 
out the  Central  West.  The  pavement  being  cheap  and  ail  these 
cities  at  that  time  having  an  unprecedented  growth,  a  much 
greater  amount  was  laid  than  would  have  been  under  ordinary  cir- 
cumstances, as  the  real-estate  boomer  desired  to  have  a  paved 
street  in  front  of  his  property  long  enough  to  sell  it,  no  matter 
what  might  be  its  eventual  life.  This  pavement  lasted  ordinarily 
about  five  years  in  good  condition,  when  the  decay  was  generally 
so  great  as  to  make  it  rough  and  undesirable  for  travel,  and  in 
a  few  years  more  it  became  practically  impassable  and  required 
renewal  when  it  had  been  down  seven  years. 

In  1888,  in  Omaha,  Des  Moines,  and  Kansas  City  there  were 
laid  pavements  practically  the  same  as  those  just  described,  except 
that  the  material  was  cypress  from  the  swamps  of  Arkansas.  This 
wood  was  much  heavier  than  cedar,  more  dense  and  compact,  and 
from  appearance  would  be  more  durable,  but  there  is  probably  no 
material  produced  by  nature  about  which  as  little  can  be  ascer- 
tained by  a  preliminary  examination  as  wood.  The  only  sure  way 
to  find  out  its  durability  is  by  experience.  In  an  actual  test  of 
abrasion,  cypress  would  probably  have  outlasted  cedar,  but  as  far 
as  decay  from  the  atmosphere  was  concerned  it  was  much  shorter- 
lived,  and  the  cypress  blocks  had  not  been  laid  more  than  two 
years  before  they  began  to  show  serious  signs  of  decay.  This  in 
itself  proved  beneficial,  as  it  prevented  a  larger  amount  from  being 


312        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

laid.  While  heart  cypress  has  deservedly  a  good  reputation  for 
durability,  the  sapling  wood  in  all  of  these  instances  plainly 
showed  itself  of  no  value. 

One  street  in  Omaha  which  was  paved  with  cypress  blocks  in 
1888  was  repaved  with  brick  in  1892,  and  the  other  streets  paved 
with  the  same  material  had  about  the  same  life. 

When  the  Tenth  Street  viaduct  in  Omaha  was  completed  in 
1889,  it  was  decided  to  pave  the  roadway  with  cypress  blocks;  but 
in  this  instance  the  inspector  went  to  the  Louisiana  swamps  to  see 
the  timber  cut  and  sawed,  selecting  only  the  best  trees,  so  that  the 
best  results  could  be  obtained.  Despite  this  precaution  the  pave- 
ment lasted  but  nine  years. 

It  is  a  well-established  fact  that  wood,  if  kept  continually  wet 
or  continually  dry,  will  last  for  almost  an  indefinite  period,  but 
when  so  situated  that  it  becomes  alternately  thoroughly  wet  and 
then  thoroughly  dry  it  will  rapidly  decay.  It  has  been  argued  by 
many,  reasoning  from  this  knowledge,  that  the  reason  why  the- 
cedar-block  pavement  in  the  West  decayed  so  much  more  rapidly 
than  some  which  had  been  laid  further  East  was  because  during 
the  summer  season  quite  a  time  elapsed  without  rain,  and  the 
blocks  became  so  thoroughly  dry  that  when  rain  did  fall  the  pore& 
were  entirely  open  and  rapidly  absorbed  the  moisture,  which,  when 
the  pavement  became  dry  again,  was  quickly  evaporated,  and  the- 
process  being  repeated,  the  wood  was  placed  under  its  worst  con- 
ditions for  durability.  While  there  is  no  doubt  that  there  may  be 
some  force  to  this  argument,  it  is  undoubtedly  true  that  cedar 
blocks  will  never  become  a  recognized  paving  material. 

In  order  to  prevent  this  decay  and  make  the  pavement  as 
durable  as  possible,  blocks  were  used  in  Michigan  from  which  all 
the  sap-wood  had  been  removed  and  were  accordingly  called  "  sap- 
less cedar  blocks/'  These  blocks  were  hexagonal  in  form  and 
could  consequently  be  laid  with  tight  joints;  but  while  their  dura- 
bility was  greater  than  the  ordinary  blocks,  the  cost  of  making 
was  so  great  that  the  advantage  was  not  enough  to  warrant  their 
general  use. 

The  city  of  Chicago,  growing  as  rapidly  as  it  has,  and  situated 
at  the  foot  of  Lake  Michigan,  where  wood  of  all  kinds  is  cheap, 
and  where  a  great  amount  of  street  pavement  must  be  laid  every 


I 

WOOD  PAVEMENTS.  313 

year,  now  uses  a  large  amount  of  cedar  blocks.  It  was  seriously 
argued,  and  with  some  force,  that,  on  account  of  its  small  first 
cost,  it  was  cheaper  to  use  cedar  blocks,  even  if  they  did  require- 
relaying  every  five  or  six  years,  than  to  lay  a  more  permanent  and 
more  expensive  pavement.  While  this  might  possibly  be  true  as. 
far  as  economy  is  concerned,  the  result  has  been  that  Chicago  has. 
had  many  miles  of  badly  paved  and  extremely  dirty  streets,  as. 
during  the  last  half  of  the  life  of  the  cedar  pavement  it  is  very 
rough  and  almost  impossible  to  keep  clean  except  at  great  expense. 
On  January  1,  1897,  Chicago  had  752.68  miles  of  cedar-block  pave- 
ment, and  during  the  year  1897  there  were  laid  23.53  miles.  On 
January  1,  1900,  the  mileage  was  763.21.  In  1897  the  average 
cost  of  this  pavement  laid  on  a  plank  base  was  70  cents  per  square 
yard,  and  when  laid  on  6  inches  of  broken  stone,  85  cents  per 
square  yard.  The  City  Engineer  at  that  time  said:  "The  plank 
foundation  is  considered  to  be  the  best,  as  the  wearing  surface  is 
more  even,  and  the  planks  last  as  long  as  the  blocks,  and  whenever 
the  pavement  is  renewed  the  street  is  torn  up,  as,  for  instance,  by 
the  gas  company  renewing  the  calking  of  their  pipes,  and  the  city 
laying  new  conduits.  In  such  cases  it  is  necessary  to  relay  the 
macadam." 

Chicago  Specifications. 

"  Upon  the  subgrade  as  above  prepared  shall  be  spread  a  layer 
of  clean  sand  not  less  than  two  inches  in  depth  over  the  entire  sur- 
face of  the  roadway. 

"  In  this  layer  of  sand  shall  be  imbedded  1  x  8-inch  sound  pine 
stringers,  extending  from  curb  to  curb  and  conforming  to  the 
grades  furnished  by  the  Engineer.  The  sand  between  the  stringers 
shall  be  thoroughly  compacted  by  ramming  and  then  struck  off 
with  an  approved  template  which  will  leave  the  top  of  the  sand 
parallel  with  and  one-quarter  inch  above  the  tops  of  the  stringers. 
The  stringers  shall  be  spaced  so  as  to  support  the  floor-planks  at 
the  ends  and  centres  thereof. 

"  On  the  stringers  and  sand  bed  constructed  as  above,  two-inch 
sound  hemlock  planks  shall  be  laid  lengthwise  with  the  street  and 
close  together.  Each  plank  must  be  firmly  bedded  throughout, 


STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

the  cracks  between  the  planks  are  to  be  filled  with  sand.  The 
flooring  when  finished  must  have  a  true  and  uniform  surface. 

"  Upon  the  plank  foundation  shall  be  set  cedar  blocks  resting 
squarely  on  their  ends  and  well  driven  together.  The  interstices 
between  the  blocks  to  be  not  less  than  three  quarters  of  an  inch 
nor  more  than  one  and  one-half  inches  in  size.  No  square  holes 
will  be  allowed. 

"  The  blocks  shall  be  of  live  cedar  free  from  bark,  perfectly 
round,,  and  not  less  than  four  inches  nor  more  than  eight  inches  in 
diameter.,  and  shall  be  six  inches  in  length.  Blocks  more  than 
eight  inches  in  diameter  must  be  split,  but  split  blocks  less  than 
three  inches  thick  cannot  be  used.  All  corners  must  be  cut  off 
from  the  split  blocks  so  as  to  make  close  joints,  and  no  two  split 
sides  shall  come  together. 

"  The  surface  of  the  pavement  must  be  true  and  uniform. 

"  The  blocks  shall  be  carefully  inspected  after  they  are  brought 
on  the  line  of  the  work,  and  all  blocks  or  other  material  which  in 
quality  or  dimensions  do  not  strictly  conform  to  these  specifica- 
tions, or  which  may  be  otherwise  defective,  shall  be  rejected  and 
must  be  immediately  removed  from  the  line  of  the  work  by  the 
contractor  or  contractors.  The  contractor  or  contractors  shall  be 
required  to  furnish  such  labor  as  may  be  necessary  to  aid  the  in- 
spector in  the  examination  and  culling  of  the  blocks  and  other 
material,  and  in  case  the  contractor  or  contractors  shall  neglect  or 
refuse  to  do  so,  such  labor  as  in  the  opinion  of  the  Board  of  Local 
Improvements  may  be  necessary  will  be  employed,  and  the  ex- 
pense incurred  shall  be  deducted  from  any  money  then  due  or 
which  may  thereafter  become  due  the  contractor  or  contractors. 

"  The  spaces  between  the  blocks  shall  be  filled  with  clean, 
screened,  dry  gravel  of  one-half  to  one  and  one-half  inches  in  size, 
the  proportion  of  said  gravel  to  be  such  as  to  completely  fill  the 
interstices.  The  gravel  shall  be  thoroughly  rammed  with  proper 
tools  and  by  competent  and  experienced  help,  and  the  interstices 
again  filled  with  the  same  kind  of  gravel  and  again  thoroughly 
rammed. 

"  In  the  above  ramming  each  interstice  must  be  struck  three 
full  blows  and  driven  down  well.  Two  competent  rammers  must 


I 

WOOD  PAVEMENTS.  315 

"be  constantly  employed  after  each  paver.  No  teams  will  be  al- 
lowed on  the  pavement  before  it  is  properly  rammed. 

"  After  ramming  the  blocks  are  to  be  covered  with  a  paving- 
pitch  which  is  the  direct  result  of  the  distillation  of  '  straight- 
run  '  coal-tar,  and  of  such  quality  and  consistency  as  shall  be  ap- 
proved by  the  Board  of  Local  Improvements.  The  pitch  must  be 
used  at  a  temperature  of  not  less  than  280°  Fahrenheit  and  be 
spread  in  such  quantity  as  to  apply  two  gallons  to  each  square 
yard  of  pavement.  The  spreading  must  be  done  in  sections  if  the 
Engineer  so  directs.  The  contractor  or  contractors  shall  provide 
the  Engineer,  or  his  representative,  with  a  duplicate  delivery- 
ticket  for  each  and  every  load  or  tank  of  paving-pitch  delivered  on 
the  work.  The  ticket  must  be  signed  by  the  consignor  of  the  pitch, 
and  be  of  a  form  approved  by  the  Board  of  Local  Improvements. 

"Immediately  after  the  spreading  of  the  paving-pitch,  and 
while  it  is  still  hot,  the  same  shall  be  covered  to  a  depth  of  not  less 
than  three-quarters  inch  with  dry  roofing-gravel,  or  gravel 
screened  from  that  used  to  fill  the  spaces  between  the  blocks.  This 
gravel  must  be  entirely  free  from  sand  or  loam,  and  not  to  exceed 
one-half  inch  in  size. 

"  All  gravel  must  be  clean,  washed,  dried,  and  heated  enough 
to  prevent  the  chilling  of  the  pitch. 

"  The  tarring  and  top  dressing  must  be  completed  each  day  to 
within  twenty-five  feet  of  the  face  of  the  blocking. 

"  If  the  blocks  that  have  been  laid,  gravelled  and  rammed 
should  become  wet  before  being  tarred  or  top-dressed,  they  must 
be  taken  up  and  reset,  without  compensation  therefor,  should  the 
Engineer  so  direct. 

"  At  the  ends  of  the  wings,  etc.,  the  pavement  must  be  pro- 
tected by  wooden  headers  consisting  of  three-inch  planks  firmly- 
secured  by  split  cedar  posts  four  feet  long,  spaced  not  more  than 
four  feet  apart." 

In  1899,  according  to  the  Department  of  Labor,  Chicago  had 
15,500,000  square  yards  of  wooden-block  pavement;  Detroit,. 
Mich.,  3,505,614  square  yards;  Superior,  Wis.,  1,360,000;  Duluth, 
Minn.,  1,140,480;  and  Milwaukee  and  Minneapolis  something  over 
one  million  square  yards  each. 


31 G        S'lUEET  PAVEMENTS  AND  PAVING  MATERIALS. 

In  the  Southern  cities  wood  pavements  have  been  laid  of  dif- 
ferent material.  San  Antonio,  Texas,  has  used  blocks  made  of 
mesquite,  hexagonal  in  form,  which  have  given  good  results,  and 
other  cities  have  tried  blocks  made  of  Osage  orange-wood.  Gal- 
veston,  Texas,  is  a  city  that  has  also  been  quoted  very  frequently 
as  having  good  wood  pavements.  In  response  to  an  inquiry  on  this 
subject  in  December,  1899,  the  City  Engineer  says: 

"  We  have  some  creosoted  pine  blocks  from  6  to  10  x  4  x  6 
inches.  About  75,000  square  yards  were  laid  in  1874,  which,  even 
now,  except  where  the  pavement  has  been  disturbed  for  street-car 
tracks,  gas-  and  water-pipes,  is  in  good  condition.  The  blocks 
were  laid  at  right  angles  to  the  sidewalk  curbs  on  a  sand  founda- 
tion, with  an  inch  space  between,  which  space  was  filled  in  with  a 
wedge  driven  down  about  2  inches  below  the  top  surface  of  the 
blocks  and  penetrating  about  2  inches  into  the  foundation  below 
the  bottom  of  the  block,  the  space  above  the  wedge  being  filled 
with  tar  and  gravel,  and  in  1892,  3,  4,  and  5  there  were  laid  some 
four  or  five  miles  of  creosoted  pine-block  pavement.  In  this  in- 
stance the  blocks  were  laid  touching  without  any  wedges,  and  tar 
was  spread  over  the  top,  and  sand  over  the  tar.  This  last  pave- 
ment has  given  endless  trouble  by  swelling  and  buckling,  and 
kicking  out  the  sidewalk  curbs  after  every  rain,  especially  when 
the  rain  followed  a  dry  spell.  I  relaid  a  couple  of  blocks  (about 
3500  square  yards)  with  wedges  and  tar  and  gravel  with  some  of  the 
displaced  blocks  about  a  year  ago,  but  it  is  beginning  now  to  show 
distress.  We  have  some  cypress  blocks,  laid  with  wedges  some  ten 
or  fifteen  years  ago,  that  did  good  service  for  eight  or  ten  years, 
"but  they  are  now  rotten  and  in  a  very  unsanitary  condition.  If 
enough  oil  is  put  in  pine  blocks  to  prevent  swelling,  I  am  satisfied 
they  would  make  excellent  paving  material  They  have  a  wonder- 
ful ability  to  resist  abrasion." 

Oakland,  Cal,  has  laid  some  pavement  of  redwood  blocks 
which  was  described  somewhat  in  detail  in  the  chapter  on  Pave- 
ments. In  arguing  in  favor  of  this  pavement  in  his  report  for 
the  two  years  ending  June  30, 1898,  the  Superintendent  of  Streets 
says  that  in  East  Twelfth  Street  in  San  Francisco,  where  2J 
inches  of  the  best  quality  of  bitumen  rock  pavement  was  com- 
pletely worn  out  twice  in  one  year,  the  property  owners  petitioned 


WOOD  PAVEMENTS.  317 

that  the  street  be  repaved  with  redwood  blocks.  At  that  time  he 
said  the  pavement  had  been  down  three  years,  without  any  ex- 
pense whatever  for  maintenance;  that  it  was  then  in  compara- 
tively good  condition,  although  showing  some  signs  of  wear,  so 
that  a  few  individual  blocks  must  be  removed  at  once.  He  adds 
that  it  was  the  success  of  this  particular  piece  of  wood  pavement 
that  induced  the  property  owners  of  Oakland  to  select  redwood 
blocks  for  East  Twelfth  Street. 

Indianapolis,  Ind.,  is  probably  the  only  city  in  the  United 
States  at  the  present  time  that  is  laying  wood  as  an  improved 
pavement. 

Mr.  M.  A.  Downing,  President  of  the  Board  of  Public  Works, 
in  a  paper  read  before  the  American  Society  of  Municipal  Im- 
provements at  Toronto,  in  1899,  describes  Indianapolis  wood  pave- 
ments in  detail.  He  claims  that  the  almost  universal  failure  of 
v.rood  in  street  pavements  in  this  country  has  been  generally  the 
fault  of  the  engineers  not  selecting  suitable  wood,  or  not  taking 
proper  precaution  to  prevent  it  from  decay.  After  studying  all 
the  wood  pavements  in  this  country  and  in  Europe,  the  Indian- 
apolis authorities  laid  red-cedar  rectangular  blocks  from  the  State 
of  Washington,  without  any  treatment.  They  were  laid  with  close 
joints  on  a  concrete  base  and  1-inch  sand  cushion.  These  pave- 
ments have  now  been  down  five  years  and  are  considerably  worn 
and  some  have  decayed.  In  1896  four  streets  were  paved  with  the 
same  material,  except  that  the  blocks  were  creosoted.  The  dimen- 
sions of  the  blocks  were  4  inches  wide  and  5  inches  deep,  and  laid 
at  an  angle  of  45°  with  the  curb.  The  joints  were  laid  close, 
and  no  provision  was  made  for  expansion  at  the  curb.  Some 
little  trouble  has  been  experienced  on  account  of  the  blocks  bulg- 
ing, and  mainly  on  streets  paved  with  the  plain  blocks,  but  some 
trouble  has  occurred  with  the  creosoted  blocks.  On  account  of 
this,  the  Board  of  Public  Works  adopted  heart-wood  of  the  long- 
leaf  Southern  yellow  pine,  with  the  block  4  inches  wide,  4  inches 
deep,  and  creosoted.  These  blocks  were  laid  as  above  described, 
except  that  a  space  of  from  1  to  2  inches  was  left  next  to  the  curb 
for  expansion.  This  space  was  filled  with  sand  and  covered  with 
hot  paving-pitch.  The  interstices  between  the  blocks  were  par- 
tially filled  with  fine,  dry  sand,  when  the  entire  surface  was  rolled 


313        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

smooth  and  then  covered  with  hot  paving-pitch  and  fine  gravel 
screenings.  These  pavements  gave  no  trouble  on  account  of  ex- 
pansion, and  although  they  have  been  laid  three  years,  no  wear  is 
noticeable.  The  Board  of  Public  Works  feel  that  the  creosoted 
pavement  has  been  a  success  in  every  way.  Its  cost  has  been  from 
$2.10  to  $2.50  per  square  yard. 

The  following  are  the  specifications  for  this  work: 

"  1.  The  wearing  surface  will  be  composed  of  creosoted  wooden 
blocks,  of  either  of  the  following  varieties  as  may  be  designated 
by  the  Board  of  Public  Works  at  the  time  of  letting  the  contract: 
Long-leafed  yellow  Southern  pine  blocks,  short-leafed  yellow 
Southern  pine  blocks,  or  hemlock  blocks.  Bidders  in  submitting 
bids  shall  submit  sample  of  each  of  the  above-named  varieties, 
and  shall  state  a  price  on  each  kind  separately.  All  blocks  shall 
be  of  sound  timber,  free  from  bark,  sap-wood,  loose  or  rotten 
knots,  or  other  defects  which  will  be  detrimental  to  the  life  of  the 
blocks  or  will  interfere  with  the  la}dng  of  the  same.  No  second- 
growth  timber  will  be  accepted. 

"2.  Blocks  shall  be  subject  to  inspection  whenever  required 
by  the  City  Engineer,  and  shall  be  in  all  respects  satisfactory  to 
him.  The  contractor  shall  furnish  all  labor  to  handle  and  cull 
blocks.  All  condemned  blocks  must  be  removed  from  the  street 
at  once. 

"  3.  After  the  blocks  have  been  inspected  and  found  satisfac- 
tory, they  shall  be  placed  in  an  air-tight  chamber,  where,  by  means 
of  superheated  steam  and  the  use  of  a  vacuum-pump,  all  sap  in 
the  blocks  shall  be  vaporized  and  then  removed.  When  the  blocks 
are  thoroughly  dry,  and  while  the  cylinder  is  under  a  vacuum  of 
fifteen  or  twenty  inches,  heavy  creosote  oil,  weighing  8.8  Ibs.  to 
the  gallon,  shall  be  admitted  into  the  cylinder  and  pressure  added 
until  the  pressure  in  the  cylinder  shall  be  at  least  fifty  pounds  per 
square  inch.  The  blocks  shall  remain  in  the  cylinder  until  they 
have  absorbed  ten  pounds  of  oil  per  cubic  foot  of  timber  and  until 
the  creosote  has  impregnated  the  timber  uniformly  'through  the 
entire  thickness  of  the  blocks. 

"  4.  The  blocks  shall  be  four  inches  in  depth  and  four  inches 
thick,  the  length  being  about  nine  inches;  the  fibre  of  the  wood 
running  in  the  direction  of  the  depth.  They  shall  be  laid  with 


WOOD  PAVEMENTS.  319 

the  length  at  an  angle  of  45°  to  the  curb,  in  courses  extending 
across  the  street.  The  blocks  in  adjoining  courses  shall  break 
joints.  The  courses  shall  be  laid  strictly  parallel  and  the  blocks 
shall  be  driven  close  together.  Where  curb  is  used  other  than  a 
form  of  combined  curb  and  gutter,  three  courses  shall  be  laid  next 
to  arid  parallel  with  the  curb. 

"  5.  The  joints  shall  be  filled  with  paving-cement  which  shall 
be  as  nearly  as  possible  to  the  condition  of  being  pliable,  not  brit- 
tle in  cold  weather,  and  so  solid  in  hot  weather  that  there  will  be 
no  tendency  to  run  out  of  the  joints.  It  shall  be  equal  or  supe- 
rior in  quality  to  a  cement  composed  of  10  per  cent  of  refined 
Trinidad  asphalt  mixed  with  90  per  cent  of  coal-tar  paving-cement, 
distilled  at  a  temperature  of  not  less  than  600°  Fahrenheit.  The 
temperature  shown  on  the  gauge  attached  to  the  cement-tank 
shall  show  not  less  than  300°  Fahrenheit  while  the  cement  is  be- 
ing applied,  and  shall  show  such  higher  degrees  as  the  Engineer 
may  direct,  if  considered  necessary  by  him  on  account  of  weather 
or  character  of  materials  used,  to  render  the  cement  fluid  enough 
to  run  into  the  joints  properly.  The  paving-cement  shall  not  be 
used  unless  the  blocks  are  thoroughly  dry.  Any  excess  of  cement 
on  the  surface  shall  be  broomed  off  so  as  to  leave  as  little  as  pos- 
sible thereon.  Great  care  must  be  taken  not  to  disfigure  the  curb, 
walks,  or  lawns  with  material,  and  any  damage  on  this  account 
must  be  repaired  by  the  contractor.  Extra  care  must  be  taken 
and  extra  material  must  be  used  at  the  gutters  and  around  catch- 
basins  or  other  structures,  in  filling  all  joints  in  both  paving  and 
curbing,  to  effectually  prevent  the  leakage  of  water  into  the  sub- 
roadway.  All  joints  shall  be  completely  filled  to  the  top  before  the 
top  dressing  is  put  on. 

"  6.  The  surface  of  the  pavement  when  completed  as  above 
shall  be  covered  with  a  one-half-inch  top  dressing  of  clean,  coarse 
sand  or  granite  screenings.  All  excessive  sand  or  granite  screen- 
ings not  to  be  taken  up  by  the  blocks  shall  be  removed  by  the  con- 
tractor, without  additional  compensation,  as  soon  as  directed  by 
the  Board  of  Public  Works  or  the  City  Engineer. 

"Note. — The  wooden  blocks  are  laid  on  a  6-inch  hydraulic- 
cement  concrete  foundation  on  which  is  placed  a  1-inch  cushion- 
coat  of  sand." 


320        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


Wood  Pavements  in  Australia. 

During  the  last  twenty  years,  Sydney,  New  South  Wales,  has 
laid  a  large  amount  of  pavement  with  the  hard  woods  of  that 
country.  The  blocks  are  3  inches  wide,  6  inches  deep,  and  9  inches 
long.  They  are  laid  generally  on  a  base  of  6  inches  of  cement 
concrete  over  which  is  spread  a  thin  layer  of  cement  mortar  mixed 
in  the  proportion  of  one  of  cement  and  two  of  sand,  so  as  to  give 
a  perfectly  smooth  surface  to  the  concrete.  The  blocks,  after 
having  been  dipped  in  tar  heated  to  the  boiling-point,  are  laid 
at  right  angles  to  the  curb,  with  a  2-inch  expansion-joint  at  the 
curb  which  is  filled  with  puddled  clay.  All  the  first  pavements 
were  laid  with  an  inch  space  between  the  courses,  the  joints  being 
filled  with  gravel  and  paving-pitch;  but  experience  soon  demon- 
strated that  the  open  joint  was  a  mistake,  as  the  edges  of  the 
blocks  broomed  and  wore  down  under  traffic,  so  that  the  surface 
soon  became  rough  and  uneven.  After  some  of  the  pavement  had 
been  laid  ten  or  eleven  years,  the  blocks,  having  shown  no  signs  of 
decay,  were  taken  up  and  the  ends  sawed  off  and  relaid  with  close 
joints. 

Many  different  kinds  of  wood  have  been  used,  and  under  ordi- 
nary traffic  the  early  pavements  wore  as  follows:  Blue  gum,  1/10 
of  an  inch  per  annum;  mahogany,  1/8  of  an  inch;  turpentine, 
1/17  of  an  inch;  beech-box,  1/7  of  an  inch;  spotted  gum,  1/7  of  an 
inch;  baltic,  1/10  of  an  inch;  colonial  cedar,  1/12  of  an  inch;  black 
butt,  1/22  of  an  inch;  red  gum,  1/10  of  an  inch. 

After  seventeen  years'  experience,  the  City  Surveyor  of  Syd- 
ney decided  that  tallow-wood,  black  butt,  blue  gum,  red  gum,  and 
mahogany  were  the  best,  the  wear  under  the  improved  methods  of 
laying  being  from  1/80  to  1/60  inch  per  annum. 

In  a  paper  read  before  the  Institution  of  Civil  Engineering  in 
1894,  Mr.  Walter  A.  Smith  gave  some  interesting  details  as  to  sev- 
eral wood-paved  streets  in  Sydney.  Martin  Place,  64  feet  wide 
between  curbs,  was  paved  with  close  joints.  The  blocks  were  of 
the  usual  size  and  laid  on  a  concrete  base  9  inches  thick,  on  which 
was  spread  a  -|-inch  coat  of  cement  mortar,  mixed  one  part  of 
cement  to  three  parts  of  sand. 

On  the  surface  thus  prepared  the  blocks  were  laid,  having  been 


WOOD  PAVEMENTS.  321 

dipped  twice  in  hot  tar  and  allowed  to  stand  two  days  for  the  sur- 
plus tar  to  drain  off.  The  blocks  were  of  tallow-wood  and  red 
mahogany.  Hot  tar  was  then  spread  on  the  surface  and  broomed 
into  the  joints,  over  which  was  spread  a  thin  coating  of  sand  and, 
before  traffic  was  allowed  on  the  street,  an  additional  coating  of 
stone  screenings.  An  expansion-joint  one  and  one-half  inches 
wide  was  left  next  to  the  curb,  and  filled  with  mastic.  The  road- 
way, although  64  feet  wide,  had  a  crown  of  3  inches  only. 

Mr.  Smith  states  that  in  joining  the  new  with  the  old  pave- 
ment, that  had  been  laid  some  six  years,  with  a  cement  joint,  the 
width  of  the  joint  being  marked  by  iron  studs  projecting  §  of  an 
inch,  it  was  found  that  dry-rot  had  set  in  wherever  the  wood  had 
been  in  contact  with  the  cement.  Although  different  kinds  of 
timber  had  been  used,  every  block  was  found  to  be  more  or  less 
affected.  This  decayed  timber  was  examined  microscopically,  but 
no  signs  of  fungoid  growth  could  be  discovered.  It  was  there- 
fore decided  that  the  dry-rot  was  caused  by  chemical  action  be- 
tween the  cement  and  the  wood.  In  another  place  where  is  was 
necessary  to  take  up  blocks  that  had  been  laid  eight  years,  where 
the  joints  had  been  filled  with  tar,  pitch,  and  stone  screenings, 
the  timber  was  found  to  be  in  a  perfect  state  of  preservation,  and 
although  the  pavement  had  sustained  a  daily  traffic  of  approxi- 
mately 25,000  tons  for  eight  years,  it  was  practically  as  good  as 
when  laid,  the  greatest  wear  observable  on  the  blocks  being  1/16 
of  an  inch. 

Mr.  Smith  states  that  in  Sydney  there  are  blocks  which  have 
been  laid  thirteen  years,  on  one  of  the  busiest  streets  of  the  city, 
which  had  only  worn  9/16  of  an  inch,  and,  from  their  condition 
^hen  examined,  seemed  to  be  good  for  ten  years'  more  service. 
He  estimates  the  life  of  the  hard-wood  pavement  in  Sydney  at  not 
less  than  twenty-one  years.  These  pavements  cost  $2.43  per  yard 
for  close-jointed  work,  and  $2.66  per  yard  with  i  or  J  asphalt 
joints,  exclusive  of  the  concrete  foundation. 

In  1895  Twentieth  Street,  New  York  City,  between  Fifth 
Avenue  and  Broadway,  was  laid  with  Australian  harri-karri  wood. 
This  pavement  was  laid  as  an  experiment,  at  the  expense  of  the 
promoters,  in  practically  the  same  manner  as  that  just  described, 
with,  an  expansion-joint  next  to  the  curb.  This  pavement  has  now 


322        STREET  PAVEMENTS  AND  PAYING  MATERIALS. 

been  in  constant  use  for  nearly  five  years,  and,  except  where  open- 
ings have  been  made,  is  practically  as  good  as  when  laid.  When  the 
work  was  being  completed,  the  supply  of  Australian  wood  was  ex- 
hausted, and  the  Fifth  Avenue  end  had  to  be  completed  with  cedar 
blocks.  This  portion  of  the  work  is  considerably  worn,  showing 
very  clearly  the  superiority  of  the  Australian  wood.  The  surface 
is  as  smooth  as  asphalt,  and  has  given  some  trouble  on  account  of 
its  slipperiness,  if  having  at  times  required  sanding.  Judging  ^rom 
this  one  small  piece  of  pavement,  the  Australian  wood  is  certainly 
a  success  as  a  paving  material. 

Chemical  Treatment  for  Timber. 

Mention  has  been  made  of  wood  paving-blocks-  that  have  been 
treated  chemically.  Whether  this  is  of  practical  benefit  or  not 
engineers  are  not  wholly  agreed.  A  careful  study  of  the  question, 
however,  would  seem  to  indicate  that  it  must  be  decided  by  existing 
conditions  in  each  case.  If  a  pavement  is  to  be  subjected  to  so 
heavy  a  traffic  that  the  blocks  will  be  worn  out  before  the  action 
of  decay  sets  in,  it  would  seem  unnecessary  to  treat  them  chemi- 
cally unless  such  treatment  would  enhance  their  wearing  qualities, 
an  effect  which  has  not  as  yet  been  demonstrated.  On  the  other 
hand,  where  traffic  is  light,  and  the  life  of  the  pavement  governed 
by  the  action  of  the  elements  rather  than  by  traffic,  any  treatment 
that  will  increase  its  durability  is  worthy  of  consideration.  Then, 
too,  some  woods  are  more  susceptible  to  treatment  than  others, 
while  some  should  be  treated  green  and  others  not  until  they  are 
seasoned,  dependent  often  upon  the  character  of  the  chemical 
used. 

There  is  not  sufficient  space,  nor  is  there  the  disposition  in  this 
work,  to  detail  at  any  length  the  different  preservatives  that  have 
been  applied  to  timber.  It  is  desirable,  however,  to  give  a  brief 
outline  of  the  industry,  showing  something  that  has  been  done, 
and  what  are  the  most  approved  methods  of  preserving  timber  at 
the  present  time. 

A  commission  appointed  to  investigate  wood  pavements  and  the 
preservation  of  wood  for  paving  purposes  reported  to  the  Mayor 
of  Boston  in  1873.  From  their  report  and  the  one  made  by  the 


WOOD  PAVEMENTS.  323 

Committee  of  the  Franklin  Institute  in  1843  many  of  the  histori- 
cal facts  herein  contained  are  taken. 

In  1657  Glauber  recommended  treating  wood  with  tar  as  a 
preservative.  In  1791  a  .patent  was  issued  to  a  Mr.  Murdock  for 
preserving  timber  from  decay  by  painting  it  with  a  mixture  of 
sulphide,  arsenic,  and  zinc.  From  that  time  on  a  great  many 
methods  have  been  proposed,  but  those  at  present  in  use  consist 
of  injecting  different  kinds  of  antiseptics  into  the  pores  of  the 
wood.  The  methods  best  known  are  those  called  "  kyanizing," 
"  burnettizing,"  and  "  creosoting."  Kyanizing  takes  its  name 
from  a  Mr.  Kyan  and  consists  of  an  application  of  corrosive  sub- 
limate which  is  injected  into  the  pores  of  the  wood.  Mr.  Burnett 
used  a  solution  of  chloride  of  zinc;  while  creosoting  consists  of 
injecting  creosote  oil.  The  last  two  are  the  methods  that  are  gen- 
erally used  at  present  both  in  this  country  and  in  England. 
Burnettizing  was  first  introduced  in  England  in  1838. 

Sulphide  of  copper  has  also  been  used  very'  successfully  in 
Europe,  but  it  is  said  that  it  cannot  be  used  under  all  circum- 
stances— that  it  protects  fully  only  green  wood  that  contains  much 
sap.  Railway  ties  laid  on  the  Northern  Eailway  of  France  in  1846 
treated  with  this  material  were  found  in  as  good  condition  as  ever 
in  1885,  while  those  untreated  had  been  replaced  some  time  before 
by  new  ones. 

An  article  in  the  Engineering  News  for  1895  describes  the  treat- 
ment adopted  by  the  Southern  Eailway  for  preserving  their  ties. 
The  timber  is  placed  in  a  strong,  tight  cylinder  in  which  a  vacuum 
is  created  and  live  steam  turned  on  until  the  temperature  is  raised 
to  125°.  A  vacuum-pump  is  then  attached  to  open  the  pores  of 
the  wood.  The  live  steam  is  admitted  the  second  time  under  a 
pressure  of  30  pounds  per  square  inch  for  six  or  eight  houM,  the 
temperature  not  exceeding  250°  Fahrenheit.  The  steam  is  again 
blown  off  and  a  third  vacuum  created,  24  to  36  inches,  and  main, 
tained  from  four  to  six  hours  at  a  temperature  of  225°.  The  cyl- 
inder is  then  filled  with  creosote  oil;  the  pumps  are  started  and 
the  pressure  raised  to  about  100  pounds  per  square  inch  and  main- 
tained for  over  two  hours,  when  the  cylinders  are  opened  and  the 
oil  drawn  off  and  the  timber  taken  out.  The  average  time  of  treat- 


324:        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

ment  for  each  charge  is  from  eighteen  to  twenty  hours,  and  the 
amount  of  oil  used  1^  gallons  per  cubic  foot  of  timber. 

In  burnettizing  the  process  is  similar  to  the  above,  except  that 
a  zinc  solution  is  used  instead  of  creosote,  and  the  steam  is  held  at 
30  pounds  for  three  and  one-half  to  six  hours  instead  of  from  six 
to  eight  hours.  The  average  time  of  this  treatment  is  from  eleven 
to  twelve  hours,  and  the  amount  of  absorption  4J  gallons  per  cubic 
foot.  The  solution  contains  1.7  per  cent  of  pure  zinc  chloride,  a 
mixture  consisting  of  34.46  pounds  stock  solution  (43  per  cent 
chloride,  2  per  cent  impurities,  and  55  per  cent  water)  to  100 
gallons  of  water.  The  officials  of  the  road  say  that  burnettizing 
makes  the  timber  hard  and  brittle,  and  for  that  reason  it  should  not 
be  used  where  it  is  subjected  to  any  strain.  Consequently  their 
practice  is  to  use  chloride  of  zinc  for  preserving  ties,  and  creosote 
for  bridge-timber,  etc. 

Mr.  Walter  W.  Curtis  read  a  paper  before  the  American  Society 
of  Civil  Engineers  on  the  17th  of  May,  1899,  on  the  preservation 
of  railway  ties  by  zinc  chlorides.  He  states  that  the  first  road  to 
adopt  the  treated  ties,  other  than  as  an  experiment,  was  the 
Atchison,  Topeka,  and  Santa  Fe  Kail  way.  This  road  built  a  plank 
for  treating  timber  chemically  in  Las  Vegas,  New  Mexico,  in  1885. 
At  first  the  Wellhous,  or  zinc-tannin,  process  was  used.  This 
process  differed  from  burnettizing  in  that  the  solution  of  zinc 
chloride  contained  a  small  amount  of  glue,  and  after  the  first  in- 
jection was  followed  by  another  composed  of  a  solution  of  tannin, 
the  effect  being,  it  was  claimed,  that  the  tannin  formed  with  the 
glue  small  particles  of  artificial  leather,  insoluble  in  water,  which 
would  fill  the  ducts  of  the  wood  and  retain  the  zinc  chloride. 

Latterly  the  burnettizing  method  has  been  used,  the  full  num- 
ber of  ties  treated  in  thirteen  years  being  about  three  million. 
The  officials  of  the  road  are  satisfied  as  to  the  value  of  the  treat- 
ment, but  are  uncertain  as  to  the  relative  values  of  zinc  tannin 
and  the  plain  zinc-chloride  methods,  the  former  costing  several 
cents  more  per  tie  than  the  latter. 

A  plant  built  in  Chicago  in  1886  treated  a  larger  number  of 
ties.  The  Chicago,  Eock  Island,  and  Pacific  Eailway  used  the 
Wellhous  process  until  1896,  when  it  was  modified  by  omitting  the 
glue  in  the  zinc  chloride  and  injecting  it  in  a  solution  by  itself 


WOOD  PAVEMENTS.  325 

followed  by  a  third  injection  of  tannin.  This  change  was  made 
because  it  was  thought  that  the  mixture  of  the  glue  with  the 
chloride  solution  decreased  its  fluidity  and  made  very  difficult  the 
injection  of  the  necessary  amount  of  chlorine. 

The  early  practice  was  to  treat  all  ties  without  regard  to  condi- 
tion as  to  soundness  or  dryness,  but  latterly  no  unsound  or  satu- 
rated ties  have  been  used. 

In  1890  the  Chicago  Tie  Preserving  Co.  treated  some  experi- 
mental ties  for  the  Duluth  and  Iron  Range  Railway.  They  Con- 
sisted of  85  ties  of  white  pine,  85  of  tamarack,  and  86  of  Norway 
pine.  They  were  cut  during  the  winter  of  1889  and  90,  treated  in 
October,  and  placed  in  the  track  almost  immediately  with  ten  each 
of  the  same  kind  untreated,  which  were  cut  at  the  same  time.  In 
1898  it  was  found  that  the  treated  ties  were  not  only  free  from 
decay,  but  were  more  dense  and  had  cut  less  under  the  rail.  It 
\vas  deemed  that  the  ties  would  last  fifteen  years  longer,  while  the 
untreated  ties  were  completely  worn  out.  The  average  of  the  un- 
treated ties  on  this  road  was  from  seven  to  eight  years. 

Mr.  Curtis  says  that  to  treat  dead  or  dozy  \vood  is  a  waste  of 
time  and  chemicals;  that  the  chloride  of  zinc  has  apparently  no 
power  to  stop  decay  which  has  already  begun,  and  it  is  doubtful 
if  any  other  treatment  is  better  in  that  respect.  In  speaking  of 
foreign  practice,  he  says  that  France  and  Great  Britain  use  the 
creosote  process  almost  entirely,  burnettizing  not  having  been  sat- 
isfactory. 

The  German  railroads  have  used  either  zinc  chloride  or  a  com- 
bination of  chloride  and  creosote,  and  sometimes  creosote  alone. 
Since  1895,  Prussia  state  railways  have  used  a  zinc-creosote  process, 
consisting  of  injecting  equal  amounts  of  zinc  chloride  and  creosote 
to  the  amount  of  1^  Ibs.  per  cubic  foot  of  timber.  He  says  that 
one  road  was  furnished  with  171,000  pine  ties  treated  with  the 
zinc-creosote  process  under  nine  years'  guarantee.  At  the  end 
of  the  nine  years  only  29  had  become  unfit  for  use,  and  none  of 
these  was  rotten.  The  cost  of  treating  these  with  chloride  of  zinc 
for  the  German  railways  in  1896  was  13  cents  for  oak,  15  cents  for 
beech,  and  16  cents  for  pine;  and  with  creosote,  21  cents  for  oak, 
50  cents  for  beech,  and  43  cents  for  pine;  while  the  average  life 


326        STREET  PAVEMENTS  AND    PAVING  MATERIALS. 

in  years  was  15,  9,,  and  12  for  chloride  of  zinc  and  24,  30,  and  20, 
respectively,  for  creosote. 

The  cost  of  burnettizing  sawed  pine  ties,  6x8  inches  by  8  feet 
long,  for  the  Southern  Pacific  Railway  was  10  cents  each  in  1893, 
and  a  little  over  6  cents  in  1897,  not  including  interest  or  deprecia- 
tion. On  the  Atchison,  Topeka,  and  Santa  Fe  Railway  the  cost  of 
zinc-tannin  treatment  has  been  about  15  cents,  and  for  1892  about 
14  cents,  and  13  cents  for  burnettizing.  In  1897  the  cost  of  the 
zinc-tannin  was  11.6  cents,  no  interest  or  depreciation  being  in- 
cluded. 

While  the  above  facts  taken  from  Mr.  Curtis's  paper  relate  to 
railroads  wholly  rather  than  to  pavements,  they  illustrate  clearly 
the  effect  of  a  chemical  treatment  upon  wood  as  a  preservative; 
and  while  the  deductions  as  to  the  action  of  wood  in  railroad-tracks 
would  not  necessarily  follow  when  applied  to  wood  pavements, 
they  are  still  of  value,  and  are  the  best  data  available  at  present. 

The  so-called  creosote  oil  of  commerce  does  not  contain  any 
creosote.  The  creosote  odor  that  comes  from  the  oil  is  caused  by 
carbolic  acid,  which,  being  soluble,  exerts  very  little  preservative 
influence  upon  the  wood. 

Creosote  is  the  product  of  the  destructive  distillation  of  wood, 
while  the  ordinary  creosote  oil  is  obtained  from  coal. 

Specifications  for  creosoting  should  provide  that  the  oil  used 
should  contain  at  least  50  per  cent  of  naphthalene,  as  that  is  what 
gives  the  oil  its  preservative  properties  both  against  the  weather 
and  the  teredo  navalis  or  other  organisms. 

The  Norfolk  Creosoting  Co.  of  Norfolk,  Va.,  has  issued  a  trade 
publication  upon  the  subject  of  creosoting.  It  is  stated  there  that 
the  preservation  of  timber  consists  of  two  distinct  operations,  the 
preparation  of  the  wood  and  its  impregnation  with  the  preservative. 
It  is  necessary  to  remove  from  the  wood  all  portions  of  the  tissue 
that  are  subject  to  fermentative  action.  This  consists  of  the  ex- 
traction of  the  liquids  and  semi-liquids  occupying  the  interfibrous 
space,  without  softening  the  cement  binding  of  the  nbrilla?,  or 
bundles  of  cellular  tissue,  forming  the  solid  or  fully  matured  part. 

If  this  step  is  conducted  at  too  low  a  temperature  or  for  too 
short  a  time,  only  the  sap  or  liquid  part  nearest  the  surface  will 
be  extracted,  leaving  insufficient  space  for  receiving  the  preserva- 


f  '• 

WOOD  PAVEMENTS.  327 

live.  If,  on  the  other  hand,  the  operation  be  carried  on  at  too 
high  a  temperature  or  for  too  long  a  time,  the  resinous  portions 
of  the  bundles  of  fibrillae  will  be  softened  and  the  wood  lose  its 
elasticity  in  just  the  proportion  that  the  coherence  of  the  fibrilla3 
is  lessened.  The  temperature  should  never  be  less  than  212°  nor 
more  than  266°  F. 

The  following  specifications  for  creosoting  are  from  the  publi- 
cation above  referred  to: 

"  Oil. — All  oil  shall  be  the  heavy  or  dead  oil  of  coal-tar,  con- 
taining not  more  than  1J  per  cent  of  water,  not  more  than  5  per 
cent  of  tar,  and  not  more  than  5  per  cent  of  carbolic  acid. 

"  It  must  not  flash  below  185°  F.  nor  burn  below  200°  F.,  and 
it  must  be  fluid  at  118°  F.  It  must  begin  to  distill  at  320°  F.,  and 
must  yield,  between  that  temperature  and  410°  F.,  of  all  substances 
less  than  20  per  cent  by  volume. 

"Between  410°  and  470°  F.  the  yield  of  naphthalene  must 
be  not  less  than  40  nor  more  than  60  per  cent  by  volume.  At  two 
degrees  above  its  liquefying-point  it  must  have  a  specific  gravity  of 
maximum  1.05  and  minimum  1.015. 

"Processes  of  Treatment. — Seasoning:  This  is  to  be  accom- 
plished by  subjecting  the  timber  to  the  action  of  live  steam  for 
a  period  of  from  five  to  seven  hours  at  a  pressure  of  35  to  55 
pounds  per  square  inch,  the  temperature  not  at  any  time  exceed- 
ing 275°  F.  unless  the  timber  be  water-soaked,  in  which  case  it 
may  reach  285°  F.  for  the  first  half  of  the  period.  At  the  expira- 
tion of  the  steaming  the  chamber  shall  be  entirely  emptied  of  sap 
and  water  by  drawing  off  at  the  bottom.  As  soon  as  the  cham- 
ber is  cleared  of  all  sap  and  water  a  vacuum  of  not  less  than  20 
inches  shall  be  set  up  and  maintained  in  the  chamber  for  a  period 
of  from  five  to  eight  hours,  or  until  the  discharge  from  the 
vacuum-pump  has  no  odor  or  taste,  the  temperature  in  the  cham- 
ber being  maintained  at  between  100°  and  130°  F.  The  chamber 
being  again  emptied  of  all  sap  and  water,  the  oil  is  to  be  admit- 
ted, the  vacuum-pump  being  worked  at  its  full  speed  until  the 
chamber  is  filled  with  oil.  As  soon  thereafter  as  is  practicable 
such  a  pressure  shall  be  set  up  as  shall  cause  the  entire  charge  of 

timber  to  absorb pounds  of  oil  within per  cent,  more  or 

less  (at  a  minimum  penetration  of  1£  inches  in  round  timber 


328        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

for  a  treatment  of  12  pounds  of  oil  per  cubic  feet,  constituting- 
a  basis  for  determining  the  penetration  due  to  a  treatment  of  any- 

specific  quantity  of  oil),  inches  from  all  exposed  surfaces. 

The  depth  of  the  penetration  being  ascertained  by  boring  the* 
treated  piece  with  an  auger  making  a  hole  not  more  than  f  inch 
in  diameter,  such  pieces  as  are  found  not  to  have  the  required 
penetration  being  returned  to  the  chamber  with  a  subsequent 
charge  for  further  treatment." 

Where  any  chemical  treatment  is  adopted,  both  in  this  country 
and  in  Europe,  it  seems  to  be  generally  accepted  that  creosote  is 
the  best  treatment;  but  Australian  woods  have  given  excellent 
results,  and  about  all  that  could  be  expected  of  any  material,  with- 
out any  treatment  whatever.  It  is  doubtful,  however,  if  any  of 
the  available  woods  of  this  country  will  give  satisfactory  results 
without  chemical  treatment  of  some  kind. 

The  experience  of  the  different  cities  that  have  tried  wood  as 
a  paving  material  has  been  such  that  a  pronounced  success  must 
be  obtained  before  it  will  be  again  taken  up  as  a  paving  material. 
Besides  its  lack  of  durability,  it  has  been  objected  to  seriously  on 
account  of  its  slipperiness  and  its  unsanitary  qualities.  The  varie- 
ties of  wood  that  have  been  used  in  this  country  have  absorbed 
water  freely,  which  has  been  as  freely  evaporated  in  warm  weather,, 
this  being  one  cause  of  its  unsanitariness.  This  objection  would 
probably  be  overcome  to  a  great  extent,  if  not  wholly,  by  chemi- 
cal treatment,  as  it  is  claimed  by  many  bacteriologists  that  no  un- 
healthy germ  exists  in  the  wood  itself;  but  it  is  extremely  doubt- 
ful, when  the  success  of  asphalt  and  brick  is  considered,  if  wood 
will  ever  come  in  favor  in  this  country  as  a  paving  material. 


CHAPTER    XI 

BROKEN-STONE   PAVEMENTS. 

As  has  been  seen  in  the  study  of  stone-block  pavements,  the 
developments  led  to  a  general  reduction  in  the  size  of  blocks. 
So  with  the  irregular  stone  pavements,  they,  too,  decreased  in 
size  as  their  use  increased.  While  probably  small  broken  stone 
were  used  in  roads  for  many  years  previous,  it  was  not  until  1764 
that  what  is  known  at  the  present  time  as  macadam  roads  were 
first  built  systematically  by  M.  Tresaguet,  a  French  engineer,  who 
was  the  first  to  adopt  this  plan,  and  it  came  into  general  use 
about  ten  years  later.  His  method  of  construction  as  described 
by  himself  is  as  follows: 

"  The  bottom  of  the  foundation  is  to  be  made  parallel  to  the 
surface  of  the  road.  The  first  bed  of  the  foundation  is  to  be  placed 
on  edge,  and  not  on  the  flat,  in  the  form  of  the  rough  pavement 
and  consolidated  by  beating  with  a  large  hammer,  but  it  is  un- 
necessary that  the  stones  should  be  even  with  one  another. 

"  The  second  bed  is  to  be  likewise  arranged  by  hand,  layer  by 
layer,  and  beaten  and  broken  coarsely  with  a  large  hammer,  so 
that  the  stones  may  wedge  together  and  no  empty  space  may  re- 
main. 

"  The  last  bed  of  3  inches  in  thickness  to  be  broken  about  to 
the  size  of  a  small  walnut  with  a  hammer  on  one  side  of  a  sort 
of  anvil,  and  thrown  upon  the  road  with  a  shovel  to  form  a  curved 
surface.  Great  care  must  be  taken  to  choose  the  hardest  stone 
for  the  last  bed,  even  if  one  is  obliged  to  go  to  more  distant  quar- 
ries than  those  which  furnish  the  stone  for  the  body  of  the  road. 
The  solidity  of  the  road  depending  on  this  latter  bed,  one  cannot 
be  too  scrupulous  as  to  the  quality  of  the  materials  which  are  used 
for  it." 

329 


330        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

The  object  of  this  lower  course  of  large  stone  was  to  separate 
the  wearing  surface  from  the  subgrade,  rather  than  to  form  a 
foundation  for  the  road. 

This  method  as  just  described  was  practically  that  adopted  by 
Telford  some  forty  years  later  in  England,  the  difference  being 
principally  in  making  the  subgrade  level  and  forming  the  crown 
with  the  stone  itself,  rather  than  making  the  base  parallel  to  the 
finished  surface  of  the  road  as  Tresaguet  did.  The  following  is 
taken  from  Parnell's  treatise  on  Roads,  which  gives  Telford's 
specifications  in  detail: 

"  Upon  the  level  bed  prepared  for  the  road  materials  the  bot- 
tom course,  or  layer  of  stone,  is  to  be  set  by  hand  in  the  form  of 
a  close,  firm  pavement.  They  are  to  be  set  on  the  broadest  edges, 
lengthwise  across  the  road,  and  the  breadth  of  the  upper  beds  is 
not  to  exceed  4  inches  in  any  case.  All  the  irregularities  of  the 
upper  part  of  the  said  pavement  are  to  be  broken  off  by  a  ham- 
mer, and  all  the  interstices  to  be  filled  with  stone  chips,  firmly 
wedged  together  by  hand  with  a  light  hammer.  The  middle  18 
feet  of  pavement  is  to  be  coated  with  hard  stone  as  nearly  cubical 
as  possible,  broken  to  go  through  a  2J-iiich  ring,  to  a  depth  of  6 
inches;  4  of  these  6  inches  to  be  first  put  on  and  worked  by 
traffic,  after  which  the  remaining  2  inches  can  be  put  on.  The 
work  of  setting  the  paving-stones  must  be  executed  with  the  great- 
est care  and  strictly  according  to  the  foregoing  directions,  or 
otherwise  the  stone  will  become  loose  and  in  time  may  work  up  to 
the  surface  of  the  road.  When  the  work  is  properly  executed,  no 
stone  can  move;  the  whole  of  the  material  to  be  covered  with  1J 
inches  of  good  gravel,  free  from  clay  or  earth." 

Parnell,  in  commenting  on  this  last  clause  of  covering  the 
road  with 'gravel,  says:  "  The  binding  which  is  required  to  be  laid 
on  a  new-made  road  is  by  no  means  of  use  to  the  road,  but,  on  the 
contrary,  is  injurious  to  it.  This  binding  by  sinking  between  the 
stone  diminishes  absolute  solidity  to  the  surface  of  the  road,  lets 
in  water  and  frost,  and  contributes  to  preventing  complete  con- 
solidation of  the  mass  of  the  broken  stone." 

A  contemporary  of  Telford  and  a  man  whose  name  has  been 
given  to  this  class  of  roads,  in  the  English-speaking  world  at  least, 
was  Macadam.  He  worked  on  very  different  principles,  in  that 


BROKEN-STONE  PAVEMENTS.  331 

he  not  only  did  not  require  the  foundation-course,  but  stated  that 
he  considered  it  positively  injurious.  He  enunciated  the  follow- 
ing principles  as  fundamental:  "  That  it  is  the  native  soil  which 
really  supports  the  weight  of  traffic;  that  while  it  is  preserved  in 
a  dry  state,  it  will  carry  any  weight  without  sinking,  and  that  it 
does  in  fact  carry  the  road  and  carriages  also;  that  this  native 
soil  must  be  previously  made  quite  dry  and  a  covering  impene- 
trable to  rain  must  then  be  placed  over  it  in  that  dry  state;  that 
the  thickness  of  the  road  should  only  be  regulated  by  the  quan- 
tity of  material  necessary  to  form  such  impervious  covering  and 
never  by  any  reference  to  its  own  power  of  carrying  weight." 

In  some  evidence  given  before  a  Parliamentray  commission 
upon  the  subject  of  roads,  soon  after  Macadam  had  taken  up  their 
reconstruction,  he  stated  in  answer  to  a  question  by  one  of  the 
committee  that  he  considered  that  10  inches  of  well-consolidated 
material  was  sufficient  to  carry  any  load,  and  that  without  any 
reference  whatever  to  the  foundation.  He  also  added  that  he 
would  prefer  a  soft  foundation  to  a  hard  one,  going  so  far  as  to 
say  that  he  would  prefer  a  bog  if  it  were  sufficiently  hard  to  allow 
a  man  to  walk  over  it.  It  must  be  remembered  that  all  of  these 
roads  were  very  different  when  first  built  from  those  of  the  so- 
called  macadam  roads  of  to-day,  as  they  received  no  rolling  what- 
ever, but  were  consolidated  wholly  by  traffic. 

The  question  as  to  which  is  the  better  system,  Telford's  or 
Macadam's,  is  one  that  has  been  discussed  for  a  good  many  years. 
It  is  hardly  necessary  to  say  that  at  the  present  time  Macadam's 
idea  of  having  a  soft,  yielding  foundation  for  his  road  is  not  con- 
sidered good  practice.  On  the  other  hand,  the  foundation  as  de- 
scribed by  Telford  is  expensive,  and  in  roads  of  light  traffic,  with 
a  good  natural  foundation,  it  would  seem  to  be  unnecessary. 
Where  a  particularly  solid  roadbed  is  required  it  is  the  custom  of 
many  engineers  to  build  what  is  called  the  telford-macadam  road, 
that  is,  it  has  a  telford  base  with  a  macadam  wearing  surface. 
Macadam's  own  particular  work,  when  he  took  it  up,  consisted  of 
repairing  old  roads  rather  than  constructing  new,  and  it  is  said 
that  he  was  so  successful  that  in  many  instances  the  cost  of  re- 
construction per  mile  was  but  little,  if  any,  more  than  had  been 
the  previous  cost  per  annum  for  maintenance,  and  it  is  also  true 


332        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

that  the  condition  of  the  roads  was  very  much  improved.  The 
roads  built  previous  to  his  time  were  very  crude,  although  con- 
taining an  immense  amount  of  material,  but  laid  with  an  entire 
lack  of  scientific  knowledge.  Macadam  describes  this  old  process 
in  vogue  at  that  time  as  follows: 

"  The  practice  common  in  England  and  universal  in  Scotland 
in  the  formation  of  a  new  road  is  to  dig  a  trench  below  the  sur- 
face of  the  ground  adjoining,  and  in  this  trench  deposit  a  quantity 
of  large  stones;  after  this  a  second  quantity  of  stones  broken 
smaller,  generally  to  about  7  or  8  Ibs.  weight.  These  previous 
pieces  of  stone  are  called  the  bottoming  of  the  road,  and  are  of 
various  thicknesses,  according  to  the  caprice  of  the  maker,  and 
generally  in  proportion  to  the  sum  of  money  placed  at  his  dis- 
posal. On  some  new  roads  made  in  Scotland  in  the  summer  of 
1819  the  thickness  exceeds  3  feet. 

"  That  which  is  properly  called  the  road  is  then  placed  on  the 
bottoming  by  putting  large  quantities  of  broken  stone  or  gravel, 
generally  a  foot  or  18  inches  thick,  at  once  upon  it,  and  from  the 
careless  way  in  which  this  is  done  the  road  is  as  open  as  a  sieve  to 
receive  the  water  which  is  retained  in  the  trench." 

This  description  allows  one  to  understand  the  radical  change 
made  by  Macadam  when  he  inaugurated  his  system.  It  can  be 
readily  seen  how,  under  any  material  amount  of  traffic,  a  road 
constructed  in  such  a  manner  might  soon  become  very  rough  and 
uneven  and  very  disagreeable  for  traffic.  When  one  thinks  of 
building  to  take  the  place  of  these  roads  others  with  a  maximum 
thickness  of  10  inches  and  made  up  of  stones  which,  according 
to  Macadam's  standard,  could  be  easily  placed  in  one's  mouth  (and 
which  should  not  weigh  more  than  6  ounces),  it  can  be  readily 
understood  that  a  Parliamentary  investigation  was  quite  in  order 
before  any  great  amount  of  money  was  expended  in  this  work. 

The  trite  saying  that  "Nothing  succeeds  like  success/'  how- 
ever, was  just  as  true  then  as  it  is  now,  and  it  required  but  a  short 
time,  and  very  little  testimony,  to  satisfy  even  the  Parliamentary 
committee  that  the  money  was  well  expended.  Macadam  utilized 
the  old  material  already  in  place,  and  by  breaking  it  as  he  did,  by 
hand,  gave  employment  to  a  large  number  of  people,  many  of 
whom,  as  he  says,  were  old  men  and  women. 


BROKEN-STONE  PAVEMENTS.  333 

In  speaking  of  the  relative  merits  of  macadam  and  telford 
roads,  Mr.  A.  J.  Cassatt,  in  a  letter  to  the  Commissioner  of  Pub- 
lic Eoads  in  New  Jersey,  says  that  as  a  result  of  his  experience 
with  both  systems,  commencing  with  the  telford,  he  is  very 
strongly  in  favor  of  the  macadam  under  any  circumstance  and  for 
any  kind  of  subgrade.  He  says  that  during  the  long  periods  of 
dry  weather  in  the  summer  the  roads  are  apt  to  disintegrate  and 
the  surface  become  covered  with  loose  stones,  and  that  this  occurs 
more  frequently,  and  to  a  greater  extent,  in  the  telford  than  in  the 
macadam.  Another  objection  he  makes  is  that  the  surface  stones 
wear  off  much  more  rapidly  with  the  solid  telford  base  than  with 
the  macadam,  which  always  wear  smoothly  and  uniformly  except 
when  the  bond  is  broken  in  the  early  spring,  when  the  frost  is 
coming  from  the  ground. 

Although  the  macadam  and  telford  roads  are  taken  up  under 
the  head  of  Pavements,  they  should  not,  strictly  speaking,  be 
classed  as  such,  as  they  are  not  suitable  for  city  streets,  although 
used  to  a  considerable  extent  in  many  large  cities  on  account  of 
their  cheapness.  Their  principal  objection  is  their  extreme  dusti- 
ness,  requiring  almost  constant  sprinkling,  which  causes  a  great 
amount  of  mud,  and  this  is  entirely  out  of  place  in  a  city  street. 
Any  one  doubting  the  advisability  of  the  macadam  for  an  urban 
district  should  visit  the  Back  Bay  section  of  Boston  on  a  windy 
day  in  winter,  when  the  ground  is  free  from  snow  and  the  weather 
too  cold  to  permit  sprinkling,  and  he  will  be  thoroughly  convinced. 
As  long,  however,  as  a  law  remains  on  the  statute-books  allowing 
a  property  owner  to  pay  for  the  first  cost  of  a  pavement  and  com- 
pelling the  city  to  pay  for  all  future  pavements,  so  long  will 
macadam  streets  be  laid,  as  thrifty  taxpayers  will  be  willing  to 
undergo  the  discomfort  of  the  dust  for  the  sake  of  avoiding  a 
heavy  assessment  for  a  good  pavement. 

The  question  involved  in  the  construction  of  a  macadam  street 
in  a  city  is  very  different  from  that  governing  the  construction  of 
a,  suburban  road;  and  while  the  general  principle  of  the  construc- 
tion is  necessarily  the  same  in  both  cases,  what  would  be  proper 
for  one  might  be  decidedly  improper  for  the  other. 


334        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Macadam  Streets. 

Before  any  street  is  macadamized  in  a  city,  it  should  be  sewered 
and  the  connection-pipes  all  laid,  so  that  the  subject  of  drainage 
would  be  taken  care  of  in  that  way.  In  some  soils,  however,  it 
might  be  necessary  to  lay  supplementary  pipes  to  take  care  of  this 
drainage;  but  it  is  fair  to  assume  that  the  surface-water  is  pro- 
vided for  before  the  street  is  ordered  improved.  This,  however,  is. 
not  always  done,  and  when  an  engineer  is  obliged  to  construct  a 
macadam  street  in  an  unsewered  section,  he  must  make  special 
provisions  for  both  surface-  and  sub-drainage.  Under  such  con- 
ditions, however,  no  macadam  pavement  should  be  laid  as  a  per- 
manent improvement,  but  only  to  make  a  temporary  roadway,  and 
not  then  for  the  entire  width  between  curb-lines. 

If  a  street  without  sewers  is  curbed,  guttered,  and  paved  for  its 
entire  width  between  curbs,  the  surface-water  is  necessarily  led  to- 
the  low  points  of  grade,  and  very  often  with  no  means  whatever 
for  taking  care  of  it.  If  the  soil  consists  of  sand  and  gravel,  tem- 
porary provision  can  often  be  made  by  digging  large  cesspools  at 
the  curb  corners  and  stoning  them  up  loosely,  so  that  the  water 
may  soak  away  gradually.  This,  however,  is  a  temporary  expedi- 
ent, but  is  the  only  thing  that  will  afford  temporary  relief,  even. 
If,  on  the  other  hand,  gutters  are  not  laid,  and  only  the  central 
portion  of  the  roadway  improved,  the  water  will  run  to  the  sides 
and  much  of  it  soak  away  in  the  ground,  rather  than  be  concentrated 
at  one  point.  If,  however,  the  streets  are  well  sewered,  with  catch- 
basins  at  low  points  of  the  grade,  the  question  of  surface-water 
is  very  simple,  and  if  drains  are  necessary  to  carry  off  the  water 
from  the  subgrade,  they  can  be  connected  with  the  catch-basins. 

Assuming,  then,  that  the  city  street  is  sewered  and  satisfac- 
torily drained,  the  questions  of  quality,  size,  and  thickness  of  th& 
material,  as  well  as  the  base,  must  be  determined.  Macadam's 
theory  that  a  road  on  an  elastic  foundation  would  last  longer  than 
one  on  a  solid  base  has  caused  considerable  amusement  among  en- 
gineers of  the  present  time,  yet  he  was  unquestionably  correct.  It 
is  a  well-known  fact  to  all  railroad  engineers  that  a  track  laid  in 
a  rock-cut,  with  the  ties  resting  on  the  solid  rock,  will  wear  out 
much  more  quickly  than  when  laid  on  a  roadbed  that  is  somewhat 
elastic,  and  also  that  the  wear  and  tear  of  the  rolling-stock  will 


t 

BROKEN-STONE  PAVEMENTS.  335 

be  appreciably  greater.  This  is  because  the  rails  are  perfectly 
rigid  and  they  themselves  must  take  up  the  impact  of  the  car- 
wheels,  which  otherwise  is  partially  transferred  to  the  elastic 
roadbed. 

It  is  also  well  known  that  if  a  stone  resting  on  an  anvil  or  solid 
rock  be  struck  a  blow  with  a  heavy  hammer,  it  will  break,  whereas, 
if  resting  on  soft  earth,  it  will  remain  unharmed  under  the  same 
blow,  but  will  be  driven  into  the  soil.  In  the  one  case,  the  reaction 
of  the  blow  is  all  taken  up  by  the  stone  which,  in  consequence,  is 
broken.  On  the  other  hand,  the  impact  of  the  blow  is  mainly  taken 
up  by  the  resistance  of  the  soil  and  the  stone  remains  unharmed. 
It  is  for  this  reason  that  both  the  rolling-stock  and  the  iron  of  the 
railroad  on  a  rigid  base  suffer  more  than  when  the  roadbed  is. 
slightly  elastic.  For  this  reason,  too,  a  road  laid  in  the  manner 
described  by  Macadam  as  to  base  will  last  longer  than  one  that, 
has  a  solid  foundation,  but  it  will  not  be  as  smooth,  nor  will  it 
maintain  its  form  as  well  under  traffic. 

It  must  be  remembered,  whenever  the  present  macadam  roads 
are  compared  with  those  built  in  the  days  of  Telford  and  Macadam,, 
that  the  vehicles  were  expected  to  do  the  work  which  in  these 
times  is  performed  by  a  steam-roller,  and  that  what  is  required  at 
the  present  is  a  good  road  as  soon  as  it  is  constructed,  as  well  as, 
one  that  is  durable;  so  that  in  a  city  street  care  must  be  taken 
to  see  that  all  soft  or  perishable  matter  has  been  removed  from 
the  subgrade,  and  the  foundation  prepared  of  some  material  that 
can  be  consolidated  under  the  roller. 

It  should  be  understood,  too,  that  any  macadam  road  (and  in 
this  connection  and  hereafter  the  term  "  macadam  "  will  be  applied 
to  all  roads  with  the  wearing  surface  made  up  of  small  broken 
stone,  the  word  telford  being  applied  only  to  the  base)  must  con- 
sist, as  do  all  other  pavements,  of  a  foundation  and  wearing  sur- 
face. Any  material  that  is  imperishable  and  can  be  easily  con- 
solidated under  the  roller  is  suitable  for  the  foundation,  and  its 
selection  must  depend  upon  the  material  at  hand.  Assuming, 
however,  as  is  generally  the  case,  that  all  the  material  for  a  city 
street  must  be  brought  from  the  outside,  where  transportation 
charges  are  comparatively  large,  the  material  that  gives  the  bes-t 
result  is  the  one  that  should  be  selected  as  a  rule.  The  thickness 


336        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

of  the  foundation  depends  upon  the  amount  of  traffic  the  street 
is  to  sustain. 

Many  engineers  differ  materially  in  the  thickness  which  is  con- 
sidered proper  for  a  macadam  pavement,  but  for  a  street  that 
has  a  moderate  amount  of  traffic,  and  where  the  pavement  is  to  be 
permanent,  it  would  seem  that  the  total  thickness  of  8  inches  would 
give  the  best  results.  The  size  of  the  stone  for  the  foundation- 
course  is  not  so  material,  provided  it  will  comply  with  the  condi- 
tions of  the  principle  laid  down  before,  that  is,  that  it  will  thor- 
oughly compact  under  the  roller.  Too  large  stones  and  those  of 
irregular  shape  will  not  give  good  results  in  that  respect.  The  size 
most  commonly  adopted  is  specified  in  a  general  way  as  being  one 
that  will  pass  through  a  3-inch  ring.  This  will  give  a  stone  slightly 
exceeding  3  inches  in  some  dimensions,  but  generally  not  enough 
to  do  any  harm.  It  should  be  solid  and  of  an  imperishable  char- 
acter. 

In  determining  the  thickness  of  the  wearing  surface,  it  must  be 
considered  not  only  how  fast  the  surface  will  wear  out,  but  also 
liow  much  it  can  be  permitted  to  wear  away  without  the  road  be- 
coming too  rough.  It  is  well  known  that  a  broken-stone  road  must 
wear  unevenly,  and  that  after  it  has  worn  down  in  that  way  to  such 
a  depth  that  the  surface  has  become  so  rough  that  new  material 
must  be  added,  any  extra  depth  that  has  been  given  to  the  wear- 
ing surface  will  be  wasted.  Thus,  if  the  general  wear  of  the  road 
has  been  3  inches  and  the  surface  is  in  such  condition  that  it  must 
be  entirely  gone  over  and  brought  up  to  the  original  grade,  the 
amount  of  wearing  surface  below  3  inches  is  of  no  benefit;  and  if 
the  wearing  surface  were  6  or  7  inches,  half  of  it  would  have  been 
wasted,  so  that  it  would  seem  that  the  proper  apportionment  is  8 
inches  of  material  divided  equally  between  the  wearing  surface 
and  the  foundation. 

Character  of  the  Wearing  Surface. 

In  determining  the  character  of  the  stone  that  is  subject  to 
traffic  different  conditions  entirely  must  be  considered  from  those 
governing  for  the  foundation-course.  If  the  stone  is  hard  and 
"wears  but  little  under  traffic,  the  pavement  will  be  rougher  than  if 
laid  with  a  softer  stone,  but  will  be  more  durable.  It  will  also  be 
less  dusty.  Without  any  question  trap-rock  is  the  best  material 


• 

BROKEN-STONE  PAVEMENTS.  337 

ior  the  surface  of  a  bi-oken  stone  pavement  if  its  wearing  qualities 
only  are  taken  into  consideration.  If,  however,  the  travel  on  a 
street  is  to  be  light  and  a  smooth,  easy  surface  is  required,  a  pave- 
ment composed  of  limestone  or  some  other  soft  material  will  often 
be  more  satisfactory.  Limestone  has  greater  cementitious  proper- 
ties than  trap-rock,  and  will  maintain  a  much  more  pleasing  surface 
under  light  traffic. 

The  size  and  shape  of  the  stone,  too,  are  of  great  importance. 
In  shape  they  should  be  as  nearly  cubical  as  possible,  and  whatever 
the  size  it  should  be  uniform.  Small  stones  wear  out  much  more 
quickly  than  large  ones.  If  they  are  mixed  indiscriminately,  and 
the  smaller  pieces  ground  into  dust  and  blown  away,  the  surface 
is  often  left  so  rough  that  the  wheels  of  vehicles  practically  jump 
from  one  stone  to  another,  rather  than  roll  over  a  continuous 
smooth  surface.  This  uniformity  in  the  size  of  the  stone  is  of 
-course  more  important  with  a  harder  material  than  with  a  soft,  as 
under  light  traffic  trap-rock  wears  very  slowly.  The  actual  de- 
cision, then,  as  to  which  is  the  proper  material  for  any  particular 
case  must  be  decided  by  the  existing  conditions,  and  while  it  must 
be  admitted  that  the  limestone  makes  the  most  agreeable  pavement 
for  light  traffic,  it  must  also  be  remembered  that  the  great  freedom 
from  dust  of  the  trap-rock  road  with  light  travel  is  a  great  argument 
in  its  favor. 

It  should  be  considered,  also,  that  when,  as  in  the  case  of  the 
<jity  streets,  the  material  must  be  brought  from  a  considerable  dis- 
tance, and  that  the  freight  on  a  ton  of  poor  material  is  the  same 
as  that  on  a  ton  of  good  material,  ultimate  economy  will  often  deter- 
mine which  is  the  proper  stone.  It  will  be  best,  therefore,  what- 
ever material  the  stone  is  composed  of,  to  make  the  size  for  the 
top  course  as  near  1-J  inches  in  every  dimension  as  possible. 

Construction. 

After  having  decided  upon  the  quality  and  amount  of  material 
required,  the  next  question  is  the  character  of  construction. 

Upon  a  roadbed  which  has  been  prepared  as  previously  de- 
scribed the  stone  which  is  to  form  the  foundation-course  should 
"be  spread  in  such  thicknesses  as  to  be  of  the  required  depth  after 
Tolling.  It  is  the  custom  of  some  engineers  to  roll  the  first  course 


338        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

until  it  is  thoroughly  consolidated.  Others,  however,  consider  that 
it  is  only  necessary  to  roll  it  enough  so  that  it  will  not  be  further 
compacted  under  the  rolling  of  the  wearing  surface,  but  will  leave 
a  somewhat  loose  rough  surface,  so  that  the  top  course  will  bond 
with  it  and  the  entire  pavement  be  of  one  piece  rather  than  of  two 
thicknesses  placed  one  upon  the  other.  This  latter  is  generally  con- 
sidered the  better  method,  although  the  first  has  many  strong 
advocates. 

After  the  stone  composing  the  second  course  has  been  evenly 
spread  to  the  required  depth,  it  should  be  rolled  by  a  roller  until 
it  has  been  almost  entirely  compacted  before  the  addition  of  any 
binder. 

This  is  important,  as  the  voids  of  the  stone  should  be  made 
as  small  as  possible,  so  that  no  great  amount  of  binder  will  be  re- 
quired. If  the  binding  material  be  scattered  over  the  stone  before 
it  has  been  rolled,  the  process  of  rolling  will  cause  it  to  mingle 
with  the  stone  and  fill  the  voids  and  separate  the  individual  stones 
from  each  other  so  that  they  will  roll  one  upon  the  other  without 
consolidating,  which  is  producing  exactly  the  reverse  result  of  what 
is  desired.  The  propriety  of  using  a  binding  material  at  all  has 
been  questioned  by  many  engineers.  Mr.  A.  F.  Rockwell  in  a  work 
called  "  Boads  and  Pavements  in  France  "  says  the  best  engineers. 
in  France  are  not  in  favor  of  any  binder,  according  to  the  prin-. 
ciple  that,  other  things  being  equal,  a  road  is  so  much  the  better 
the  less  fine  material  it  contains.  He  further  says  that  the  passage 
of  a  10-ton  steam-roller  forty  or  fifty  times  over  a  given  point 
renders  all  binding  material  superfluous  and  compacts  the  stone 
so  thoroughly  that  it  becomes  a  mass  nearly  as  solid  as  the  rock 
itself. 

If  this  be  true  in  France,  the  experience  of  American  engineers 
with  trap-rock  has  been  very  much  to  the  contrary.  In  the  early 
roads  in  the  time  of  Macadam,  as  is  well  known,  the  practice  was 
to  allow  traffic  to  consolidate  the  road  and  no  binder  was  used,, 
but,  about  1830,  rollers  came  into  use,  at  first  drawn  by  horses,  but 
afterwards  propelled  by  steam,  and  then  the  question  of  finishing 
the  surface  assumed  a  different  aspect. 

Mr.  Deacon,  an  engineer  of  Liverpool,  in  speaking  of  the  effect 
of  binding  material  says:  "  Under  a  15-ton  steam-roller,  preceded 


BROKEN-STONE  PAVEMENTS  339 

by  a  watering-cart,  1200  yards  of  trap-rock  macadam  without 
blinding  can  only  be  moderately  consolidated  by  27  hours'  con- 
tinuous rolling.  If  blinded  with  trap-rock  chippings  from  the 
•stone-breaker,  the  same  area  may  be  moderately  consolidated  by 
the  same  roller  in  18  hours.  If  blinded  with  silicious  gravel  from 
J  inch  in  size  to  a  pin's  head,  mixed  with  about  \  part  macadam 
sweepings  obtained  in  wet  weather,  the  surface  may  be  thoroughly 
consolidated  in  9  hours.  Macadam  laid  according  to  the  last  method 
wears  better  than  that  laid  by  the  second,  and  that  laid  by  the 
second  much  better  than  that  laid  by  the  first." 

English  engineers,  and  American  as  well,  think  that  it  is  neces- 
sary to  use  some  binding  material  in  order  to  get  satisfactory  re- 
sults; arguing  that  in  case  of  consolidation  without  binder  being 
added,  the  stones  will  not  consolidate  until  a  certain  amount  of 
dust  has  been  worn  from  them  by  the  attrition  of  the  roller,  and 
that  if  an  outside  binder  be  used,  the  road  will  be  as  solid  and  a 
great  amount  of  wear  of  the  stone  saved  for  traffic. 

Just  how  much  binder  will  be  required  depends  upon  its  char- 
acter. The  less  that  is  used,  provided  good  results  can  be  obtained, 
the  better.  It  should  be  scattered  over  the  surface  of  the  road  in 
advance  of  the  roller,  and  not  dumped  in  piles  and  then  spread,  as 
in  the  latter  case  too  great  an  amount  will  almost  always  be  used 
in  spots.  The  sprinkling-cart  should  follow  the  spreading  of  the 
material  on  the  road,  washing  it  into  the  voids,  and  the  sprinkling 
should  be  immediately  followed  by  the  steam-roller.  Care  should 
be  taken  not  to  cover  at  any  time  the  entire  surface,  as  the  binder 
would  then  serve  as  a  cushion  for  the  stone  and  prevent  the  wheels 
of  the  roller  from  acting  directly  upon  the  surface.  This  action 
of  spreading  the  binder,  sprinkling  and  rolling,  should  continue 
until  the  road  is  thoroughly  consolidated. 

If  a  surplus  of  binder  is  used,  it  not  only  prevents  the  storfe 
from  being  properly  consolidated,  but  after  the  traffic  is  allowed 
upon  the  street,  and  it  begins  to  receive  its  consolidation  from 
it,  this  surplus  binder  is  forced  up  through  the  interstices  of 
the  stone  of  the  surface  and  forms  mud  in  wet  weather  and  dust 
in  dry,  and  must  be  constantly  cleaned  from  the  surface  until  the 
street  has  become  consolidated  by  traffic. 

Just  how  much  rolling  is  required  to  make  a  solid  roadbed 


340        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

depends  upon  the  solidity  of  the  foundation,  the  character,  size> 
and  shape  of  the  stone,  and  the  character  and  amount  of  binder 
used.  Keferring  to  the  principle  of  Macadam  that  a  road  will 
wear  out  more  quickly  with  a  solid  than  with  an  elastic  foun- 
dation, it  is  equally  true,  and  for  the  same  reason,  that  a  macadam 
road  will  be  consolidated  much  more  quickly  if  the  subgrade  is. 
unyielding.  In  such  cases  the  action  of  the  roller  is  direct  upon 
the  stone  and  its  work  is  much  more  quickly  accomplished.  This, 
is  often  seen  when  macadam  is  built  in  part  upon  an  old  roadbed 
and  in  part  upon  an  ordinary  earth  base.  The  difference  in  the. 
amount  of  rolling  required  on  each  is  very  marked. 

The  character  of  the  stone  itself,  however,  is  an  important 
factor,  as  the  softer  the  stone  the  quicker  it  consolidates.  Lime- 
stone, for  instance,  with  a  binder  of  sand  or  limestojne  screenings- 
will  become  compacted  under  less  than  one-half  the  amount  of 
rolling  required  with  trap-rock  of  the  same  size. 

The  size  and  shape  of  the  stone  also  have  an  important  bear- 
ing upon  the  labor  of  consolidation.  If  the  pieces  be  cubical  and 
of  approximately  the  same  size,  they  wedge  closely  with  each 
other  and  become  thoroughly  compacted;  whereas  flat  stones  will 
continually  tip  under  the  roller  and  be  compressed  without  being 
bound  together. 

The  proper  material  for  binding  has  been  discussed  to  a  con- 
siderable extent.  When  it  is  considered  that  the  object  of  the 
binder  is  only  to  serve  as  a  cementing  material  to  hold  the  pieces 
of  stone  together,  and  at  the  same  time  make  the  surface  water- 
tight, it  would  seem  that  the  material  which  would  serve  this  pur- 
pose with  the  least  amount  of  rolling  would  be  the  best,  because 
the  cheapest,  if  the  first  cost  of  each  should  be  the  same.  Sand, 
limestone  screenings,  and  trap-rock  screenings,  as  well  as  certain 
kinds  of  clay  and  loam,  have  all  been  used  in  different  places  and 
by  different  engineers  as  binding  material.  Ordinarily  sand  is. 
the  cheapest,  as  it  can  generally  be  found  nearer  to  the  work  than 
the  stone  of  which  the  pavement  is  composed,  but  it  produces  a 
road  that  will  be  very  dusty  under  traffic,  as,  in  order  to  possess 
any  cementing  properties,  it  must  contain  a  certain  amount  of 
loam.  Clean,  sharp,  fine  sand  will  give  no  binding  effects,  as  the 
pieces  of  stone  will  simply  roll  in  the  sand  without  consolidating. 


BROKEN-STONE  PAVEMENTS.  341 

Limestone  screenings  give  excellent  results,  as  they  possess  in 
themselves  first-class  cementing  properties  and  give  a  hard  and 
smooth  surface  to  the  road.  If,  however,  the  wearing  surface  is 
composed  of  trap-rock,  most  engineers  wish  the  binding  material 
to  be  composed  either  of  trap-rock  screenings  or  a  mixture  of 
trap-rock  screenings  and  sand.  Mixed  in  the  proportion  of  3  of 
screenings  to  2  of  sand,  good  results  can  be  obtained. 

Trap-rock  in  itself  has  very  little  cementitious  value.  If  the 
binder  be  composed  entirely  of  this  material,  it  will  require  a  great 
amount  of  rolling  and  a  free  use  of  water,  but  the  result  will  be 
a  hard,  compact,  durable  road.  It  will  not  be  so  elastic  as  the 
limestone,  but  more  durable.  It  will  also  require  much  more  roll- 
ing. 

The  different  qualities  of  limestone  vary  much  in  the  amount 
of  rolling  required.  The  so  called  Tomkins  Cove  limestone,  of 
which  a  great  amount  is  used  in  the  vicinity  of  New  York  City, 
has  a  wonderful  cementing  value  and  is  easily  made  into  a  smooth, 
compact  road.  It  breaks  with  a  very  nearly  cubical  fracture  and 
is  an  almost  ideal  stone  for  a  light-traffic  road,  as  it  always  wears 
smoothly  and  presents  a  pleasing  surface  to  vehicles;  but  from 
the  very  fact  that  it  is  easily  bound  and  wears  smoothly,  it  wears 
more  rapidly  than  the  other  stones  and  consequently  is  not  as 
durable  upon  heavy-traffic  streets. 

The  amount  of  rolling  that  has  been  actually  given  in  the  con- 
struction of  different  streets  varies  greatly.  Mr.  Rockwell,  in 
his  work  previously  referred  to,  says  that,  assuming  a  layer  of 
stone  to  be  3  inches  thick  and  that  a  10-  or  12-ton  roller  is  used, 
it  is  sufficient,  with  ordinary  limestone,  for  the  roller  to  pass  over 
the  surface  50  times,  with  granite  50  to  75  times,  and  with  porphyry 
or  trap  90  to  100  times.  He  adds  that  the  amount  required  in- 
creases with  the  thickness  of  the  layers,  but  not  in  proportion  to 
the  thickness,  and  that  it  is  more  if  the  stones  are  rolled  dry  than, 
if  they  are  wet. 

American  engineers,  in  specifying  the  amount  of  rolling  re- 
quired, generally  say  that  the  street  shall  be  rolled  to  the  satisfac- 
tion of  the  engineer  in  charge.  In  France  the  engineers  have 
attempted  to  be  somewhat  more  specific  and  have  sought  to 
measure  it  by  the  number  of  ton-miles  per  square  yard;  ranging 


342        STREET  PAVEMENTS  AND   PAVING  MATERIALS. 

ordinarily  from  0.4  to  0.6  ton-mile  per  yard.  This,  however, 
while  it  takes  into  account  the  weight  of  the  roller,  does  not  con- 
sider its  speed;  that  is,  a  10-ton  roller  passing  over  a  street  at  the 
rate  of  4  miles  an  hour  would,  according  to  that  rule,  have  twice 
the  efficiency  of  one  moving  at  the  rate  of  2  miles  per  hour,  but 
it  is  hardly  probable  that  in  practice  that  result  would  be  obtained. 
At  the  same  time,  a  roller  moving  at  the  rate  of  4  miles  an  hour 
would  probably  do  much  more  effective  work  than  one  moving  at 
the  rate  of  2  miles,  but  there  seem  to  be  no  specific  data  whatever 
to  be  obtained  on  this  particular  point.  A  standard,  however,  can- 
not be  set  up  that  will  be  satisfactory  without  taking  into  consid- 
eration both  the  speed  and  weight  of  the  roller. 

In  a  piece  of  work  containing  about  18,000  square  yards  of 
macadam,  composed  of  two  courses  each  4  inches  in  thickness,  a 
careful  account  of  the  rolling  was  kept,  and  the  average  amount 
rolled  per  day  was  almost  exactly  200  square  yards,  the  material 
being  limestone  for  the  first  course  and  trap-rock  for  the  second, 
with  trap-rock  screenings  for  binding  material.  Wherever,  as  in 
this  case,  the  wearing  surface  and  binding  material  'are  both  com- 
posed of  trap-rock,  the  binder  must  be  practically  a  flour  when 
the  road  is  being  finished.  If  it  be  coarse,  the  stone  will  not  be 
cemented  together;  but  if  thoroughly  rolled  and  wet  so  that  the 
trap-rock  flour  is  flooded,  it  will  form  a  paste  which,  when  dried 
out,  will  make  a  smooth,  solid,  and  impervious  surface.  If  the 
traffic  on  such  a  street  be  light,  the  pavement  will  probably  pick 
up  slightly  under  travel  at  first;  but  if  it  be  rerolled  in  a  short  time 
after  being  opened  to  traffic,  it  will  take  its  final  consolidation 
and  prove  very  satisfactory. 

A  certain  road  in  Morris  County,  N".  J.,  was  built  12  feet  wide 
of  trap-rock,  in  two  courses  of  2J  and  1J  inches  in  thickness  re- 
spectively, and  finished  with  trap-rock  screenings.  This  was  com- 
pacted at  a  rate  not  to  exceed  200  square  yards  per  day. 

In  a  discussion  on  road-building  before  the  American  Society 
of  Civil  Engineers  in  the  latter  part  of  1898,  Mr.  E.  W.  Harrison 
of  Jersey  City,  N".  J.,  detailed  to  some  extent  the  construction  of 
the  Hudson  County  Boulevard  in  New  Jersey.  This  road  was 
theoretically  12  inches  deep  with  an  8-inch  telford  base  and  4 
inches  of  macadam,  all  of  trap-rock.  The  macadam  was  made  up 


f 

BROKEN-STONE  PAVEMENTS.  343 

*)f  two  courses  of  2^-  and  1^-inch  stones  that  would  pass  a  2^-inch 
ring,  and  the  surface  was  finished  with  trap-rock  screenings,  ex- 
cept in  one  portion  where  a  small  amount  of  clay  was  used  between 
two  layers  of  stone.  Water  was  used  freely  and,  according  to  the 
records  kept  of  the  rolling,  the  road  had  been  gone  over  from  100 
to  115  times. 

In  a  paper  on  the  Construction  and  Maintenance  of  Roads,, 
presented  to  the  American  Society  of  Civil  Engineers  in  1879, 
Mr.  E.  P.  North  mentioned  some  repairs  on  the  Southern  Boule- 
vard, New  York  City,  where  trap-rock  broken  to  pass  a  2-inch  ring 
was  laid  6  inches  thick  in  one  course,  and  38.2  hours'  rolling  was 
given  per  1000  square  yards.  He  says:  "Allowing  the  speed 
to  have  been  1£  miles  per  hour,  the  work  done  on  it  amounted  to 
0.859  ton-mile  per  square  yard  and  5.177  ton-miles  per  cubic 
yard.  201  trips  were  made  over  the  surface.  The  work  was  done 
in  July  and  August,  and  a  little  less  than  0.6  of  a  cubic  foot  of 
water  per  square  yard  was  used  for  compacting  and  puddling. 
About  J  screenings  were  added." 

In  a  consular  report  it  is  stated  that  in  Dresden  a  steam-roller 
weighing  from  10,000  to  15,000  kilograms  can  compact  from  80 
to  100  cubic  yards  per  day. 

The  amount  of  binder  required  to  properly  consolidate  a  road 
•can  be  approximately  estimated.  Assuming  the  voids  in  the  stone, 
as  it  is  ordinarily  delivered  .on  the  street,  to  be  45  per  cent,  and 
that  under  the  action  of  the  roller  these  voids  will  be  reduced  one- 
half,  there  will  still  remain  22.5  per  cent  voids  which  should  be 
filled  by  the  binder  in  order  to  have  the  road  thoroughly  solid  and 
compact.  This  would  give,  then,  approximately  25  per  cent  of  the 
amount  of  stones  spread  loosely  on  the  street  to  fill  voids.  Any 
amount  very  much  in  excess  of  this  would  seem  to  indicate  that 
the  road  was  not  thoroughly  compacted  unless  an  appreciable 
^quantity  was  left  upon  the  surface.  In  carrying  on  the  rolling  the 
work  should  be  begun  at  the  sides,  working  towards  the  centre. 
Otherwise  the  street  when  completed  is  liable  to  be  more  flat  than 
is  desired. 


344:        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Crown. 

The  principle  governing  the  amount  of  crown  to  give  a 
macadam  street  is  somewhat  different  from  that  governing  one 
of  stone  or  asphalt.  While  the  surface  of  a  macadam  road  should 
be  made  solid  and  impervious  to  water,  it  is  not  always  done,  and 
the  street  should  receive  as  much  crown  as  possible  without  hav- 
ing a  tendency  to  drive  traffic  to  the  centre  of  the  street.  The 
element  of  slipperiness  which  must  be  considered  on  the  side 
slope  of  a  hard-surface  street  can  be  entirely  eliminated  on  the- 
macadam.  Then,  too,  the  water  should  be  carried  from  the  road- 
way into  the  gutter  as  quickly  as  possible  to  prevent  any  washing 
of  the  surface.  This,  on  steep  grades,  is  very  important,  as,  in  a. 
heavy  storm,  water  running  over  the  surface  of  the  macadam  will 
do  much  more  damage  than  a  great  amount  of  traffic,  so  that,  con- 
trary to  the  rule  for  the  stone  pavement,  the  crown  of  steep  grades 
should  be  greater  than  that  of  light  ones. 

The  cementitious  properties  of  stone,  while  very  important, 
have  not  received  much  systematic  investigation,  especially  in  this 
country.  The  Massachusetts  Highway  Commission,  however,  has 
been  making  experiments  to  determine  this  during  the  past  five 
or  six  years.  The  test  which  was  finally  adopted  is  the  impact 
test,  to  which  briquettes  made  of  the  dust  of  the  different  kinds 
of  stone  to  be  tested  are  subjected.  These  briquettes  are  made 
of  the  dust  that  has  passed  through  a  screen  with  100  meshes  per 
inch  and  is  obtained  either  from  the  abrasion  test  or  by  specially 
powdered  stone.  The  briquettes  are  circular  in  section,  0.98  inch 
in  diameter  and  the  same  in  height. 

The  dust  is  placed  in  a  metal  die  of  the  proper  dimension,  and 
mixing  with  it  enough  water  to  moisten  the  dust  (0.24  cubic  inch), 
a  closely  fitted  plunger  is  inserted  on  top  of  the  wet  dust  and  sub- 
jected to  a  pressure  of  1422  pounds  per  square  inch.  The  weight 
of  the  dust  varies  with  the  density  and  compressibility  of  the 
stone,  generally  requiring  about  0.9  ounce  of  dust  to  make  a  bri- 
quette of  the  above  dimensions.  Two  weeks  should  be  allowed  for 
the  briquettes  to  dry,  at  the  ordinary  temperature  of  a  room. 

A  machine  for  testing  these  briquettes  consists  of  a  hammer 
weighing  2.2  Ibs.,  arranged  like  a  hammer  on  a  pile-driver,  on  two- 


BROKEN-STONE  PAVEMENTS.  345 

vertical  guides.  The  hammer  is  raised  by  a  screw  and  dropped 
automatically  from  any  desired  height.  It  falls  on  the  plunger, 
which  rests  upon  the  briquette  to  be  tested.  The  plunger  is  bolted 
to  a  cross-head  and  guided  by  two  vertical  rods.  A  small  lever 
carrying  a  pencil  at  its  free  end  is  connected  with  the  side  of  the 
cross-head  by  a  link  motion  arranged  so  that  it  gives  a  vertical 
movement  to  the  pencil  six  times  as  great  as  the  movement  of 
the  cross-head.  The  pencil  is  pressed  against  the  drum,  and  its 
movement  is  recorded  on  a  slip  of  paper  fastened  thereon.  The 
drum  is  moved  automatically  through  a  small  angle  at  each  stroke 
of  the  hammer.  In  this  way  a  record  is  obtained  of  the  move- 
ment of  the  hammer  after  each  blow.  The  standard  fall  of  the 
hammer  for  the  test  is  0.39  inch,  and  the  blow  is  repeated  until 
the  bond  of  cementation  of  the  material  is  destroyed.  The  final 
blow  is  easily  ascertained,  for,  when  the  hammer  falls  on  the 
plunger,  if  the  material  beneath  it  can  withstand  the  blow,  the 
plunger  rebounds.  If  not,  the  plunger  stays  at  the  point  to  which 
it  is  driven.  The  automatic  record  which  is  obtained  from  each 
briquette  is  filed  for  future  reference.  The  number  of  blows  re- 
quired to  break  the  bond  of  cementation,  as  described  above,  is 
taken  as  representing  the  binding  power  of  each  stone,  and  is  so- 
used in  comparing  this  property  in  road  materials. 

Another  material  that  is  used  in  the  vicinity  of  New  York  City 
for  binding  and  for  surface  covering  is  Koa  Hook  gravel.  This 
material  comes  from  up  the  Hudson  Eiver  and  is  possessed  of  re- 
markable cementitious  properties.  It  is  found  in  sizes  that  are 
large  enough  to  make  the  roadbed  complete  if  desired,  and  when 
screened  to  the  desired  size  makes  the  finest  finishing  for  any 
macadam  road.  It  has  been  used  to  a  great  extent  on  the  drive- 
ways of  Central  Park,  Manhattan,  and  Prospect  Park,  Brooklyn  r 
and  makes  a  surface  that  is  probably  as  good  as,  if  not  better  than, 
any  other  finishing  material  to  be  obtained  in  this  country.  Be- 
cause it  is  easily  bound  and  cemented  it  wears  rapidly,  and  on 
account  of  its  actual  cost  and  its  rapid  wear  it  makes  a  doubly 
expensive  material.  It  is  a  luxury,  and  for  park  driveways  or 
bicycle  paths  it  forms  a  surface  that  cannot  be  improved  upon. 


346        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


Finishing  the  Roadway. 

The  amount  of  fine  material  that  is  to  be  left  upon  a  finished 
roadway  is  something  upon  which  engineers  differ.  If  any  ap- 
preciable quantity  remains,  it  receives  the  action  of  the  traffic  and, 
acting  as  a  cushion,  prevents  to  a  certain  extent  the  wear  of  the 
stone;  but  it  will  be  excessively  dusty  unless  sprinkled,  and  if 
sprinkled  enough  to  prevent  dust,  is  liable  to  form  mud.  On  the 
other  hand,  if  only  enough  is  left  to  fill  the  interstices,  the  action 
of  the  traffic  comes  directly  on  the  stone,  and  the  wear  is  con- 
tinual with  the  amount  of  traffic.  It  would  seem  better,  there- 
lore,  to  put  on  a  quantity  that  will  actually  cover  the  surface  of 
the  road,  and  not  very  much  more,  and  when  this  amount  becomes 
worn  down  or  blown  away  renew  it.  In  this  way  a  less  amount 
of  sprinkling  will  be  required,  the  wear  on  the  pavement  will  be 
reduced,  and  as  little  dust  as  possible  result  from  the  traffic. 

Sprinkling. 

After  the  stones  have  become  compressed  and  the  binder  has 
been  applied,  the  road  should  be  constantly  sprinkled  with  water 
at  the  time  of  the  rolling,  and  continued  as  long  as  the  rolling  is 
in  progress.  The  water  is  necessary  both  to  wash  the  binder  into 
the  interstices  of  the  stone,  and  also  to  aid  it  in  cementing  the 
individual  stones  together.  If  the  work  can  be  carried  on  during 
a  mild  rain,  excellent  results  will  be  obtained;  but  should  excessive 
rain  or  excessive  sprinkling  at  any  time  cause  the  roadbed  to  be- 
come soft  and  yielding,  the  rolling  should  be  at  once  stopped  until 
the  subgrade  has  had  sufficient  time  to  dry  out;  for  with  a  soft 
roadbed  the  rolling  will  not  only  do  no  good,  but  it  will  absolutely 
do  harm,  as  the  earth  under  the  stones  will  be  formed  into  mud 
by  the  action  of  the  stones  in  contact  with  it,  and  the  mud  will  be 
gradually  forced  up  between  the  stones,  which  will  cause  the  road  to 
be  loose  even  after  it  is  dried  out  and  has  been  rolled.  Continual 
sprinkling,  too,  shows  whether  the  road  has  been  made  water- 
tight, as  the  wave  which  the  engineers  generally  specify  shall  form 
in  front  of  the  roller  before  the  rolling  shall  cease  will  not  be  pro- 
duced if  the  road  is  porous  and  allows  the  water  to  soak  away. 


I 

BROKEN-STONE  PAVEMENTS.  347 

Gutters. 

On  any  street  that  is  paved  with  macadam,  gutters  of  some 
sort  must  be  provided,  as  there  is  probably  no  action  that  will 
cause  more  disintegration  or  greater  injury  to  macadam  than  wrater 
flowing  over  it;  so  that  a  runway  for  the  water  must  be  provided 
of  a  different  material  if  the  street  is  paved  from  curb  to  curb,  or, 
if  no  curb  is  set,  to  provide  a  shoulder  for  the  gutter.  This 
matter,  however,  will  be  taken  up  in  detail  in  a  subsequent  chapter. 

Fig.  18  represents  a  cross-section  of  a  macadam  pavement. 


FIG.  18. 

Specifications. 

The  city  of  Providence,  R.  I.,  has  a  large  amount  of  streets 
paved  with  macadam  which  have  given  satisfaction.  The  stone 
is  purchased  by  the  city'  and  the  construction  of  the  pavement 
carried  out  by  day's  labor.  The  following  is  taken  from  the 
instructions  issued  by  the  City  Engineer  to  the  foreman  having 
charge  of  this  work: 

"  If  the  subgrade  is  too  sandy  to  admit  of  rolling,  cover  it  with 
a  thin  layer  of  loom  or  gravel  of  sufficient  thickness  to  permit 
rolling.  Pave  the  gutters  in  a  sand  bedding,  and  back  them  well 
with  coarse-sized  broken  stone;  the  paving  and  backing  to  be 
thoroughly  rammed. 

"  Put  on  the  roadway  a  layer  of  medium-sized  broken  stone; 
this  layer  is  to  be  so  placed  as  to  leave  the  roadway  surface  true 
to  section  and  about  2^  inches  below  finished  surface  after  com- 
pacting. 

"  Roll  with  the  steam-roller  until  this  layer  is  shaped  to  given 
section  and  sufficiently  firm  to  admit  of  driving  over  without  pick- 
ing up;  then  put  on  the  roadway  a  layer  of  broken  stone  of  sizes 
varying  from  one-half  to  one  and  one-quarter  inches;  this  layer  tc» 


348        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

be  so  placed  as  to  leave  the  roadway  surface  true  to  section.  Roll 
thoroughly  with  the  steam-roller,  the  road  metal  to  be  kept  damp 
while  rolling.  If  open  spaces  appear  in  the  stones  when  finishing 
rolling,  put  on  sufficient  fine  stones  to  just  fill  the  open  space.  The 
roadway  is  to  be  left  true  to  section  when  finished." 

Boston,  Mass.,  is  another  city  which  also  has  a  large  number 
of  macadam  streets,  many  of  them  in  the  heart  of  the  city,  and 
some  of  them  with  very  steep  grades.  The  following  is  taken  from 
the  Boston  specifications  for  macadam  with  telford  base,  as  far  as 
relates  to  the  construction  of  the  roadway: 

"  SECT.  6. — Telford  Base. — (a)  In  the  excavation  for  the  road- 
way is  to  be  laid  the  telford  base,  made  as  follows:  Sound,  hard 
stones,  four  inches  to  ten  inches  in  width,  eight  inches  to  twenty 
inches  in  length,  and  not  less  than  ten  inches  in  depth,  are  to  be 
placed  by  hand,  vertically  on  their  broad  edge  and  lengthwise 
across  the  roadway,  so  as  to  form  a  close,  firm  pavement;  the  pro- 
jections of  the  stones  above  an  even  surface  are  to  be  broken  off  by 
hand  and  hammer,  and  used,  with  other  stones  of  proper  size  and 
shape,  as  wedges,  to  firmly  wedge  the  stones  of  the  base  in  proper 
position,  so  that  the  surface  of  the  base  will  be  parallel  to  the  sub- 
grade  for  the  roadway  and  eight  inches  a^bove  it;  the  base  is  then 
to  be  thoroughly  rolled  with  a  steam-roller. 

"  SECT.  7. — Macadam  Surface. — (a)  Upon  the  telford  base  is  to 
be  laid  the  macadam  surface,  made  as  follows:  Hard,  durable 
broken  stones,  which  will  pass  through  a  screen  with  2^-inch  round 
holes,  and  will  not  pass  through  a  screen  with  one-inch  round  holes, 
and  are  free  from  round  or  other  ill-shaped  or  improper  stones, 
are  to  be  spread  over  the  whole  surface  of  the  base,  and  thor- 
oughly rolled  and  packed  with  a  fifteen-ton  steam  road-roller  of 
approved  pattern,  until  the  surface  is  one-half  inch  below  the 
finished  roadway;  the  spaces  between  these  stones  are  then  to  be 
filled  with  fine  screenings  or  binding-gravel  applied  in  at  least 
three  layers;  each  layer  thoroughly  worked  in  by  wetting  and 
rolling,  as  aforesaid  before  the  next  layer  is  applied,  and  during 
the  operation  the  surface  is  to  be  brought,  with  the  broken  stone, 
to  the  grade  and  shape  of  the  finished  roadway,  and  smooth,  free 
from  waves  or  other  irregularities;  only  the  teaming  necessary  for 
distributing  the  screenings,  and  for  rolling  and  wetting,  is  to  be 


f 

BROKEN-STONE  PAVEMENTS.  349 

allowed  over  the  broken  stone  after  it  is  spread  on  the  base,  and 
no  teaming  is  to  be  allowed  over  the  finished  surface  for  at  least 
three  days  after  it  is  finished." 

Extract  from  Brooklyn  Specifications. 

"  (4)  Macadam  Pavement. — On  the  foundation  for  the  mac- 
adam pavement  prepared  as  heretofore  described  and  after  thor- 
ough rolling  with  a  ten-ton  steam-roller,  there  shall  be  spread  a 
layer  of  trap-rock  or  limestone  of  such  size  that  all  of  it  will  pass 
through  a  circular  revolving  screen  having  holes  three  inches  in 
diameter  and  be  retained  by  a  similar  screen  with  holes  two  inches 
in  diameter. 

"  If  limestone  be  used  it  shall  be  tough,  hard,  and  uniform  in 
color,  and  must  not  contain  more  than  thirty  per  cent  of  lime. 
Trap-rock  used  in  the  lower  or  finishing  course  must  be  of  uni- 
form quality,  free  from  sap,  seams,  and  other  imperfections.  It 
shall  be  tough  and  not  too  brittle,  and  approximately  cubical  in 
form.  Any  lot  of  stone  containing  a  noticeable  proportion  of 
stones  whose  length  is  more  than  twice  their  breadth  will  be  re- 
jected. 

"  This  course  shall  be  of  such  depth  as  will  provide  a  thick- 
ness of  four  inches  when  consolidated.  It  shall  then  be  rolled 
with  a  steam-roller  weighing  not  less  than  ten  tons,  beginning  at 
the  sides  and  rolling  towards  the  centre,  until  the  stone  is  entirely 
compacted  and  does  not  move  under  the  roller. 

"  After  this  rolling  a  second  course  of  trap-rock  and  of  such 
size  that  all  of  it  will  pass  through  a  circular  revolving  screen 
having  holes  two  inches  in  diameter  and  be  retained  by  a  similar 
screen  having  holes  three-quarters  of  an  inch  in  diameter  shall 
fte  spread  upon  the  roadway  to  such  depth  as  will  give  a  thickness 
of  four  inches  after  thorough  rolling,  and  the  surface  shall  con- 
form exactly  with  the  section  shown  on  the  profile  plan.  During 
the  rolling  of  this  course  screenings  of  trap-rock  and  selected 
-coarse  sand  or  gravel  shall  be  spread  upon  the  stone  in  small 
quantities  and  washed  in  with  a  sprinkler.  The  trap-rock  screen- 
ings shall  be  free  from  dirt  and  other  foreign  matter,  and  shall  vary 
in  size  from  one-half  inch  to  dust,  and  about  twenty  per  cent  must 


350        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

be  what  is  known  as  trap-rock  dust  or  flour.  The  sand  must  be> 
coarse  and  only  of  such  quality  as  may  be  approved  by  the  Com- 
missioner of  Highways.  Samples  of  this  sand  must  be  submitted 
to  and  approved  by  the  said  Commissioner  before  it  can  be  used. 

"  Not  less  than  six  parts  of  the  trap-rock  screenings  to  four 
parts  of  the  sand  shall  be  used  as  a  binding  and  filling  material. 
The  screenings  and  sand  shall  be  placed  upon  the  roadway  only 
in  such  quantities  as  will  fill  the  interstices,  but  leave  no  loose 
material  upon  the  surface.  Should  an  excess  of  fine  material  at 
any  time  be  placed  upon  the  roadway,  it  shall  be  swept  off  by  hand- 
brooms  before  the  work  will  be  allowed  to  proceed.  The  rolling 
of  this  course  shall  be  continued  until  the  roadway  is  perfectly 
solid  and  compact. 

"  A  finishing  course  consisting  of  trap-rock  screenings  and 
selected  sand  in  the  proportions  above  described  shall  then  be 
spread  over  the  roadway  so  that  it  completely  covers  the  surface. 
This  course  shall  be  rolled  and  sprinkled  simultaneously  until  it 
is  brought  to  proper  form  and  grade  and  is  so  hardened  and  bound 
that  it  will  not  pick  up  under  travel." 


Roads. 

Although  the  question  of  road-building  has  been  discussed  to 
a  considerable  extent  in  this  country,  for  many  years  only  the 
States  of  Massachusetts,  New  Jersey,  and  New  York  have  under- 
taken road-building  systematically  and  as  a  work  of  the  State.  In. 
Massachusetts  the  first  Act  was  passed  by  the  Legislature  in  1893. 
The  work  was  all  under  the  charge  of  a  Highway  Commission  ap- 
pointed by  the  Governor  and  which  has  general  charge  of  approxi- 
mately all  road-building  under  this  Act.  A  certain  amount  is 
appropriated  by  the  Legislature  each  year,  being  $600,000  in  1896 
and  $800,000  in  1897,  a  portion  of  which  is  repaid  to  the  State  as 
follows: 

"  One-quarter  of  any  money  expended  under  provision  of  this 
Act  in  any  county  of  the  highway,  with  interest  on  said  one-quar- 
ter at  the  rate  of  3  per  cent  per  annum,  shall  be  repaid  by  the  said 
county  to  the  Commonwealth  in  such  reasonable  sums  and  at  such 


•m 

BROKEN-STONE  PAVEMENTS.  351 

times  within  six  years  thereafter  as  the  State  Commission,  with 
the  approval  of  the  State  Auditor,  shall  determine.  Taking  into 
consideration  the  financial  condition  of  the  county,  the  Treasurer 
and  Receiver-General  shall  apply  all  money  so  repaid  to  the  pro- 
portion to  be  expended  by  such  Commission/' 

Under  this  law  a  great  many  miles  of  macadam  road  have  been 
built,  and  the  general  scheme  for  a  good  road  system  throughout 
the  State  has  been  adopted  and  is  being  carried  out  as  rapidly  as 
time  and  money  will  admit. 

In  New  Jersey  what  is  known  as  the  "  State  Aid  Road  Law  " 
was  passed  in  1891.  This  law  placed  the  superintendence  of  the 
construction  of  the  roads  built  under  this  Act  in  the  hands  of  the 
Commissioner  of  Public  Roads.  Section  4  provides: 

"  That  one-third  of  the  cost  of  the  roads  constructed  in  this 
State  under  this  Act  shall  be  paid  for  out  of  the  State  Treasury, 
provided  that  the  amount  so  paid  shall  not  in  any  one  year  ex- 
ceed the  sum  of  $100,000.  If  one-third  of  such  cost  shall  appear, 
by  the  statements  filed  in  any  one  year  with  the  State  Commis- 
sioner of  Public  Roads,  to  exceed  the  said  sum  of  $100,000,  then 
and  in  such  event  the  said  sum  of  $100,000  shall  be  apportioned 
by  the  Governor  and  State  Commission  of  Public  Roads  amongst 
the  counties  of  the  State  in  proportion  to  the  cost  of  the  roads 
constructed  therein  for  such  year  as  shown  by  the  statements  of 
costs  filed  in  the  office  of  the  State  Commissioner  of  Public 
Roads.  The  Governor  and  said  State  Commissioner  of  Public 
Roads  shall,  between  December  15th  and  31st  in  each  year  certify 
to  the  State  Comptroller  the  amount  to  be  paid  to  each  county  for 
such  year,  and  the  State  Comptroller  shall  thereupon  draw  his. 
warrants  in  favor  of  the  respective  county  collectors  for  the  sums 
certified  as  aforesaid  upon  the  State  Treasurer,  who  shall  pay  the 
sum  out  of  any  moneys  in  the  State  treasury  not  otherwise  appro- 
priated." 

The  report  of  the  Commissioner  of  Public  Roads  in  New  Jer- 
sey for  the  year  1897  states  that  in  1893-94  there  were  built,  pre- 
sumably under  this  law,  74.76  miles;  in  1895,  46.27  miles;  in  1896, 
51.38  miles;  in  1897,  66.5  miles. 

The  subject  of  good  roads  was  discussed  in  New  York  with 
such  force  that  it  resulted  (March  24,  1898)  in  the  passage  of  a 


352        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

law  to  provide  for  the  improvement  of  the  public  highways.  Sec- 
tion 9  of  this  law  reads: 

"  One-half  of  the  expense  of  the  construction  thereof  shall  be 
paid  by  the  State  Treasurer  upon  a  warrant  of  the  Comptroller 
issued  upon  requisition  of  such  engineer  out  of  any  specific  appro- 
priations made  to  carry  out  the  provisions  of  this  Act.  And  one- 
half  of  the  expense  thereof  shall  be  a  county  charge  in  the  first 
instance,  and  the  same  shall  be  paid  by  the  county  treasurer  of  the 
county  in  which  such  highway  or  section  thereof  is,  upon  the 
requisition  of  such  engineer;  but  the  amount  so  paid  shall  be  ap- 
portioned by  the  board  of  supervisors,  so  that  if  the  same  has  been 
built  upon  a  resolution  of  said  board  without  petition,  thirty-five 
per  centum  of  the  cost  of  construction  shall  be  a  general  county 
charge,  and  fifteen  per  centum  shall  be  a  charge  upon  the  town' 
in  which  the  improved  highway  or  section  thereof  is  located;  and 
if  the  same  has  been  built  upon  a  resolution  of  said  board  after 
petition  as  provided  in  Sec.  2,  thirty-five  per  centum  shall  be  a 
general  county  charge,  and  fifteen  per  centum  shall  be  assessed 
upon  and  paid  by  the  'Owners  of  the  lands  benefited  in  proportion  to 
the  benefits  accruing  to  said  owners  as  determined  by  the  town 
assessors  in  the  next  section  hereof." 

The  supervision  of  this  work  is  placed  in  the  hands  of  the  State 
Engineer,  and  the  amount  of  work  which  can  be  performed  de- 
pends entirely  upon  the  State  appropriation,  which  the  first  year 
was  only  $50,000,  while  the  petitions  for  the  time  that  that  ap- 
propriation was  available,  if  granted,  would  have  involved  the  con- 
struction of  356  miles  of  road,  which,  at  the  cost  of  $10,000  per 
mile,  would  have  meant  an  expenditure  on  the  part  of  the  State  of 
$1,680,000,  when  only  $50,000  was  provided. 

Road-construction. 

Although  nearly  everything  that  has  been  said  concerning  the 
construction  of  macadam  on  city  streets  could  also  be  said  with 
the  same  force  about  macadam  roads,  there  are  a  great  many  other 
things  that  must  be  taken  into  consideration  by  the  engineer  when 
he  is  about  to  build  a  broken-stone  road  in  a  suburban  or  country 
district.  In  the  one  case,  the  engineer  is  generally  given  the  limits 


i 

BROKEN-SI  ONE  PA  YEMENIS.  353 

of  the  street  on  which  it  is  proposed  to  lay  the  pavement,  and  his 
province  is  to  provide  specifications  that  will  give  the  most  satis- 
factory results  for  that  particular  street.  The  question  of  cost, 
while  entering  to  a  certain  extent,  is  not  the  ruling  principle.  On 
the  other  hand,  in  road-construction  the  engineer  is  generally  given 
a-  certain  amount  of  money  which  is  to  be  expended  to  connect  two 
given  points  with  a  satisfactory  road  at  the  lowest  possible  expense, 
and  the  engineer  who  can  accomplish  this  with  the  best  results  is 
the  best  man  for  the  community. 

In  order  to  solve  this  question  of  getting  the  greatest  amount 
of  value  from  a  given  sum,  the  engineer  must  study  the  case  from 
all  points  of  view.  He  must  consider  the  amount  and  character 
of  travel,  whether  a  road  is  desired  that  will  provide  the  most 
comfort  to  those  using  it,  or  one  that  shall  be  the  most  useful. 
Both  of  these  points  will  have  a  bearing  on  the  selection  of  the  par- 
ticular material  to  be  used. 

As  has  been  said  pertinently  by  an  engineer  who  has  given  this 
matter  a  great  deal  of  study,  "  a  road  is  valuable  for  its  length 
rather  than  for  its  width  and  thickness,"  and  the  engineer  who  can 
build  the  longest  satisfactory  road  for  a  specified  amount  has  best 
solved  the  problem.  The  most  important  questions  which  he  will 
have  to  decide  in  this  connection  will  be  the  width  and  depth  of 
the  road  to  be  improved,  and  the  character  of  the  material  to  be 
used. 

Drainage. 

However  he  may  decide  these  questions,  he  must  provide  for 
a  good  roadbed.  This  cannot  be  accomplished  without  drainage, 
and  in  doing  so  he  must  take  care  of  both  the  surface  and  subsoil 
water:  the  latter  so  as  to  prevent  the  moisture  from  coming  up 
from  below  and  soaking  the  subgrade,  allowing  it  to  freeze  solidly 
in  cold  weather,  and  heave  and  soften  the  road  metal  when  it 
thaws  in  the  spring.  If  the  subgrade  be  kept  free  from  moisture, 
this  will  not  happen.  This  is  plainly  shown*  by  the  action  of  the 
frost  in  all  soils  that  allow  the  water  to  flow  freely  through  them. 
No  better  instance  of  it  can  be  seen  than  in  the  alluvial  soil  of 
Nebraska,  where  during  severe  cold  spells  it  is  a  common  occur- 


354        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

,rence  to  see  cracks  in  the  road  from  ^  inch  to  1  inch  in  width, 
caused  by  the  contraction  of  the  earth,  yet  on  account  of  the  lack 
of  moisture  no  heaving  or  disturbance  is  caused  when  the  frost  is 
coming  out  in  the  spring.  In  that  section  cottages  are  often  built 
upon  the  surface  of  the  ground,  the  only  underpinning  being 
sufficient  masonry  to  level  up  the  surface,  and  no  trouble  is  ever 
caused  by  the  heaving  of  the  earth  when  the  frost  comes  out. 

The  surface-water  must  be  taken  care  of.  Otherwise  it  will 
settle  on  -the  road  and  soften  it  and  cause  the  trouble  already 
described  by  the  alternate  freezing  and  thawing.  This  principle, 
too,  was  well  understood  by  Telford  and  Macadam,  who  always 
provided  for  drainage,  and  their  practice  has  always  been  followed 
by  engineers  since  their  time. 

This  subject  has  been  considered  so  thoroughly  and  so  intel- 
ligently by  the  Chief  Engineer  of  the  Massachusetts  Highway  Com- 
mission in  his  instructions  to  resident  engineers  that  the  following 
quotation  is  made  from  his  report  for  the  year  1896: 

Drains. 

"  82.  Where  telfording  is  used,  or  where  ground-water  from  a 
side  hill  may  work  injury  to  the  road,  you  will  build  drains. 

"  83.  If  the  road  passes  through  a  cut,  you  will  place  a  drain 
on  each  side. 

"  84.  If  the  road  is  on  a  side  hill,  you  will  place  a  drain  on  the 
up-hill  side  only. 

"  85.  All  drains  must  be  carried  to  a  proper  outlet,  either  to  a 
culvert,  to  another  drain,  or  through  the  bank. 

"86.  Where  it  is  necessary  to  extend  a  drain  to  an  outlet  be- 
yond the  section  needing  to  be  drained,  you  will  lay  the  pipe  with 
cement  joints  on  such  extension,  and  omit  the  gravel  or  stone  in 
the  trench. 

"87.  Where  a  pipe  is  carried  through  a  bank,  the  outlet  must 
be  protected  by  masonry,  as  provided  in  pipe  culverts. 

"88.  All  pipe  must  be  laid. true  to  a  line  and  grade,  and  no 
pipe  is  to  be  laid  on  a  grade  of  less  than  three  inches  in  one  hun- 
dred feet. 

"  89.  If,  in  laying  out  a  drain,  you  find  the  trench  is  likely 


BROKEN-STONE  PAVEMENTS.  355 

to  exceed  five  feet  in  depth  below  the  finished  grade,  you  will 
immediately  report  the  conditions  in  writing  to  the  Chief  Engineer. 

"  90.  The  centre  of  the  pipe  in  all  drains  will  be  placed  twelve 
inches  outside  of  the  line  of  broken  stone. 

"91.  When  the  grade  of  the  finished  road  is  three  inches  or 
more  to  the  hundred  feet,  the  bottom  of  the  drain-trench  must  be 
three  and  one-half  feet  below  the  finished  surface  of  the  road  at 
that  part  of  the  cross-section. 

"  92.  The  drain-trench  will  be  excavated  to  a  width  of  twelve 
inches  at  the  bottom  and  fifteen  inches  at  the  top,  and  should  be 
excavated  only  as  fast  as  the  drain  can  be  finished. 

"  93.  On  the  bottom  of  this  trench  you  will  place  two  inches 
of  gravel  or  broken  stone  which  will  pass  through  a  one-half-inch 
mesh. 

"  94.  All  side-drain  pipe  will  be  five-inch  salt-glazed  vitrified 
clay  pipe,  with  bell  and  spigot  joint  (unless  stated  to  the  con- 
trary in  the  specifications). 

"  95.  The  pipe  is  to  be  laid  on  the  grade  hereinbefore  men- 
tioned, with  open  joints  and  the  bell  end  toward  the  rising  grade. 

"  96.  Gravel  or  broken  stone  of  the  sizes  already  described 
will  be  filled  about  the  pipe  and  over  it  to  a  depth  of  one  foot. 
This  must  be  carefully  tamped  about  and  rammed  over  the  pipe. 
The  remainder  of  the  trench  is  to  be  filled  with  stone  which  will 
pass  through  a  three-inch  and  not  through  a  one-inch  mesh.  Grea't 
care  must  be  taken  to  prevent  any  sand,  silt,  or  earth  from  getting 
into  the  pipe  or  the  interstices  of  the  stone  in  the  trench. 

"  97.  The  subgrade  of  the  road  is  to  have  a  regular  slope  to 
the  edge  of  the  drain. 

"98.  The  price  per  linear  foot  includes  the  cost  of  trenching 
and  refilling  with  gravel  or  broken  stone,  the  cost  of  the  pipe  and 
laying,  as  well  as  all  incidental  work. 

"99.  No  allowance  will  be  made  on  extra  size  of  pipe  in  any 
drain  unless  the  larger  pipe  has  been  ordered  in  writing  by  the 
Chief  Engineer." 

Having  prepared  a  base,  the  next  thing  w-ill  be  the  determin- 
ing of  the  width  and  depth  of  the  road.  In  determining  upon 
the  width  of  the  road  to  be  improved,  the  engineer  should  first 
decide  from  the  amount  of  traffic  which  it  is  liable  to  have, 


356        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

whether  it  is  necessary  to  have  the  roadway  wide  enough  to  accom- 
modate two  lines  of  travel.  If  the  width  for  one  line  is  sufficient, 
it  will  be  a  waste  of  material  to  make  the  road  any  wider  than  will 
well  accommodate  one  line  of  vehicles.  Two  trucks  with  5  feet 
width  of  wheel-base  and  9  feet  width  of  load  meeting  can  pass  on 
a  16-foot  roadway  with  a  clearance  of  1  foot,  assuming  the  outer 
wheels  of  each  to  go  within  6  inches  of  the  edge  of  the  macadam, 
so  that  a  width  of  16  feet  would  be  ample  to  allow  loaded  teams. 
£  feet  wide  to  meet  and  pass  without  any  wheels  going  off  from 
the  macadam.  Such  a  case  as  this,  however,  rarely  occurs,  and  if,, 
as  generally  happens,  the  road  is  in  the  vicinity  of,  and  tributary 
to,  a  large  city,  the  loaded  trucks  will  almost  all  be  going  in  one 
direction,  when  there  will  be  no  difficulty  in  the  unloaded  ones, 
turning  out  and  passing  outside  of  the  improved  portion  of  the 
road.  So  that  it  would  seem  that,  except  in  extreme  cases,  a  width 
of  16  feet  would  certainly  be  enough,  and  generally  one  of  10  or 
12  feet  if  only  one  line  of  traffic  is  to  be  provided  for. 

Even  then,  however,  the  road  should  not  be  too  narrow.  It 
should  be  sufficiently  wide  to  allow  traffic  considerable  lateral 
motion,  so  that  the  wheels  will  not  travel  uniformly  in  the  same- 
lines  and  thus  form  ruts;  but  as  the  wheel-base  of  the  ordinary 
trucks  does  not  often  exceed  5  feet  in  width,  a  roadway  10  or  12 
feet  wide  will  be  ample  in  this  regard.  . 

The  improved  portion  of  the  roads  as  constructed  by  the 
Massachusetts  Highway  Commission  is  15  feet  wide  and  upwards. 
In  a  report  of  that  Commission  for  1898  a  table  is  given  showing 
the  width  actually  travelled  on  these  roads.  The  average  width 
commonly  travelled  on  forty-six  of  the  roads  15  feet  wide  was  9 
feet  7  inches.  It  would  seem,  therefore,  that  while  a  width  of  10 
feet  would  not  have  been  sufficient  to  accommodate  that  traffic,, 
a  width  of  12  feet  would  have  been,  as  any  width  that  is  provided 
and  not  used  is  so  much  loss.  The  New  Jersey  roads  are  many  of 
them  only  10  or  12  feet  wide,  and  these  have  given  the  best  of  sat- 
isfaction. 

The  depth  of  the  road  must  be  determined  upon  practically 
on  the  same  principle  as  that  laid  down  in  the  construction  of 
street  pavements.  The  foundation  must  be  sufficient  to  sustain 
the  traffic,  and  the  wearing  surface  sufficient  to  bear  traffic  an 


BROKEN-STONE  PAVEMENTS.  357 

economical  length  of  time.  It  is  the  practice  of  some  engineers  to 
make  the  centre  of  the  road  thicker  than  the  sides,  as  the  centre 
naturally  takes  more  traffic  than  any  other  portion,  and  in  that 
way  the  entire  surface  of  the  pavement  will  be  worn  out  approxi- 
mately at  the  same  time.  In  many  cases  this  is  good  practice. 

The  Massachusetts  roads  are  built  with  a  thickness  of  6  inches, 
after  having  been  thoroughly  consolidated  and  finished  to  an  arbi- 
trary grade.  New  Jersey  roads  vary  in  thickness  from  4  to  1£ 
inches  according  to  the  traffic  the  road  is  expected  to  sustain.  In 
Queens  County,  L.  I.,  the  heaviest-traffic  roads  are  built  8  inches 
thick  in  the  centre  and  6  inches  on  the  sides,  and  for  the  lighter- 
traffic  roads  the  thickness  is  4  inches  spread  loose,  the  contractor 
being  paid  per  cubic  yard  for  the  stone  used. 


Character  of  the  Stone. 

In  determining  upon  the  stone  to  be  used  in  a  country  road, 
the  engineer  will  often  find  it  cheaper  to  use  a  poorer  grade  of 
stone,  which  is  close  at  hand,  even  if  it  does  require  more  frequent 
renewal,  than  to  transport  a  harder  and  more  durable  stone  from 
a  longer  distance.  There  is  one  disadvantage,  however,  in  using 
the  ordinary  crushed  field-stone  in  highway  construction.  The 
different  stones  vary  so  much  in  degree  of  hardness  that  the  wear 
of  the  road  is  liable  to  be  uneven  and  cause  more  frequent  renewal 
and  a  greater  cost  of  maintenance  than  if  the  stone  had  all  come 
from  one  ledge  and  been  of  uniform  material. 

It  must  be  remembered,  however,  that  certain  kinds  of  con- 
struction are  permissible  in  country  roads  that  would  not  be  in 
city  streets,  for,  while  not  desirable,  the  amount  of  dust  and  mud 
which  would  be  almost  prohibitive  in  the  city  can  be  allowed  often 
on  a  country  road  without  serious  discomfort.  So,  too,  variations 
in  sizes  of  stone  can  be  allowed,  and  if  the  traffic  be  heavy,  larger 
stone  than  could  be  used  in  a  city  pavement.  The  Massachusetts 
Highway  Commission  has  studied  this  question  very  thoroughly 
and  its  results  are  here  given: 

"  The  State  highways  are  divided  as  follows,  with  reference  to 
broken  stone  (sizes  given  are  in  inches): 


358        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

"  a.  Of  trap-rock,  bottom  course  to  be  1 J  to  2^  inches,  top 
course  to  be  \  to  1^  inches. 

"  b.  Of  trap-rock,  both  courses  to  be  1J  to  2%  inches. 

"  c.  Local  stone  other  than  trap,  bottom  course  to  be  1^  to  2J 
inches,  top  course  to  be  -|  to  1J  inches. 

"  d.  Local  stone  other  than  trap,  both  courses  to  be  ^  to  2^ 
inches. 

"  e.  Bottom  course  of  local  stone  other  than  trap,  J  to  2^ 
inches;  top  course  of  trap-rock,  \  to  1J  inches. 

"  f.  Bottom  course  of  local  stone  other  than  trap,  J  to  2% 
inches;  top  course  of  trap-rock,  1J  to  2%  inches. 

"  g.  All  trap-rock.  Bottom  course  to  be  ^  to  1^  inches,  top 
course  to  be  1J  to  2^  inches. 

"  h.  Local  stone  other  than  trap,  bottom  course  to  be  \  to  2% 
inches,  top  course  to  be  1J  to  2J  inches." 

These  different  classes  are  used  on  different  roads  according  to 
the  character  of  the  traffic  and  the  stone  which  is  available. 

It  will  be  noticed  that  all  of  the  sizes  for  trap-rock  range  from  1 J 
to  2 J,  except  in  one  case,  and  that  the  local  stone  ranges  from  J  inch 
to  2£,  the  idea  being  that  the  trap  must  in  almost  every  case  be 
transported  a  considerable  distance,  and  consequently  none  but  the 
best  size  would  be  used,  while  the  local  stone,  being  near  at  hand 
and  easily  provided  for  repairs,  is  used  in  as  small  sizes  as  J  inch, 
the  idea  being  in  this  case  to  utilize  the  entire  product  of  the 
crusher,  as  the  finishing  course  and  binder  were  always  formed  of 
the  same  material  as  the  top  course.  In  this  way  the  most  economi- 
cal results  are  obtained,  and  these  conclusions  certainly  show  a 
thorough  and  conscientious  study  of  the  subject. 

In  classes  e,  /,  g,  and  h  it  will  be  noticed  that,  contrary  to  the 
usual  custom,  the  lower  course  is  smaller  than  the  upper.  This 
is  where  the  traffic  is  heavy  and  it  is  not  considered  desirable  to 
use  larger  stone  than  2J  inches,  which  will  sustain  traffic  better 
than  a  smaller  size.  In  order  to  utilize  the  entire  output  of  the 
crusher,  it  was  necessary  to  make  the  lower  course  of  the  smaller 
size. 

This  Commission  has  also  made  very  extensive  and  scientific 
tests  as  to  the  character  of  the  different  kinds  of  stone  which  are 
valuable  for  use  in  the  vicinity  of  their  roads. 


BROKEN-STONE  PAVEMENTS.  359 

The  specimen  to  be  tested  consists  of  at  least  30  Ibs.,  to  be  a  fair 
representation  of  the  stone  to  be  supplied,  to  contain  one  piece 
3  x  4  inches  on  each  face  and  to  be  about  2  inches  thick,  and  the 
remainder  of  the  stone  to  be  the  largest-size  stone  coming  from, 
the  crusher.  The  tests  made  have  been  the  abrasion  and  the 
•cementation  tests  previously  described.  The  description  of  the 
testing-machine  for  abrasion  is  taken  from  the  report  for  the  year 
1898: 

"  It  is  constructed  entirely  of  cast  iron,  which  greatly  lessens 
its  cost.  With  this  new  machine  and  new  methods  of  obtaining 
results,  two  tests  a  day  can  be  completed,  whereas  with  the  old 
machines  it  was  possible  only  to  complete  three  in  a  week.  For  the 
.abrasion  the  machine  consists  of  four  cylinders  each  7.9  inches  in 
depth.  Each  of  these  cylinders  is  closed  at  one  end  and  has  a 
tightly  fitting  cover  for  the  other.  They  are  fastened  to  the  shaft 
so  that  the  axis  of  each  cylinder  is  at  an  angle  of  30°  with  the 
.axis  of  rotation  on  the  shaft.  The  shaft  which  holds  the  cylinders 
is  supported  by  bearings,  and  at  one  of  its  ends  is  a  pulley  by 
which  the  cylinders  are  revolved,  and  at  the  other  a  revolution- 
counter. 

"  The  stones  employed  in  making  the  abrasion  test  are  about 
the  size  used  in  making  macadam  roads — between  2J  inches  and 
1J  inches  in  diameter.  In  making  the  test  11  Ibs.  of  stone  of  the 
above  dimension  and  perfectly  clean  are  placed  in  one  of  the  cyl- 
inders. The  cover  is  then  bolted  on  and  the  cylinder  rotated  at 
the  rate  of  2000  revolutions  per  hour  for  five  hours.  Four  tests 
-can  be  made  at  once  by  using  four  cylinders.  At  each  revolution 
of  the  shaft  the  fragments  of  stone  are  thrown  twice  from  one 
end  of  the  cylinder  to  the  other,  which  grinds  them  against  one 
another  and  against  the  walls  of  the  cylinder.  After  10,000  revo- 
lutions have  been  made  the  machine  is  stopped,  the  cylinder 
opened,  and  the  contents  placed  on  a  sieve  having  -inch  meshes. 
The  material  that  passes  through  the  sieve  is  put  aside  for  the 
•cementation  test.  The  sieve  and  remaining  fragments  of  stone 
are  then  held  under  running  water  until  all  the  adhering  dust  is 
washed  off.  After  these  remaining  fragments  have  thoroughly 
•dried  they  are  carefully  weighed  and  their  weight  subtracted  from 
11  Ibs.  original  weight  of  all  the  stones  of  the  test.  The  difference 


360        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

obtained  is  the  weight  of  the  detritus  under  T^  inch  worn  off 
by  the  test.  The  percentage  of  the  -inch  detritus  may  be  taken, 
as  the  coefficient,,  or  the  coefficient  adopted  by  the  National  School 
of  Eoads  and  Bridges  of  France  may  be  used.  The  latter  has  been 
adopted  by  the  Commission  and  may  be  obtained  by  the  formula 

Coefficient  of  wear  =  20  X  7*7  —  ~yy> 

where  W  is  the  weight  in  grams  of  detritus  under  -^  inch  in  size 
obtained  from  2.2  Ibs.  of  stone,  used. 

A  table  is  given  showing  the  results  of  221  tests  made  for 
abrasion  and  cementation,  and.  from  the  table  it  is  found  that  in 
sixteen  samples  of  trap-rock  the  coefficient  of  wear  ranged  from 
15.03  to  26.93  with  an  average  of  19.85,  and  for  the  cementation 
value  from.  11  to  62,  with  an  average  of  29.  On  forty-four  samples- 
of  field-stone  the  coefficient  of  wear  ranged  from  5.43  to  19.19, 
with  an  average  of  11.70,  and  the  cementation  value  from  6  to 
46,  with  an  average  of  17.7. 

In  five  samples  of  granite  the  coefficient  of  wear  ranged  from 
8.41  to  17,90,  with  an  average  of  13.56,  and  for  cementation  value 
from  5  to  14,  with  an  average  of  8.8;  while  four  limestone  ranged 
for  coefficient  of  wear  from  8.26  to  17.20,  with  an  average  of  11.78, 
and  cementation  value  from  10  to  23,  with  an  average  of  15. 

In  the  above  instances  the  cementation  value  and  coefficient  of 
wear  are  derived  from  the  same  stone. 

The  Massachusetts  Highway  Commission  provides  that  where 
the  subsoil  is  of  impervious  clay,  telford  base  shall  be  used,  laid 
on  a  gravel  foundation.  After  the  top  of  the  telford  is  formed 
and  the  space  partly  filled  up,  broken  stone  is  spread  over  the  entire- 
surface  and  rolled  solidly  into  the  telford.  This  practice  is  not 
sanctioned  by  many  engineers,  as  they  prefer  to  leave  the  telford 
more  or  less  open  to  provide  for  drainage;  but  when,  as  in  this 
case,  it  is  laid  on  a  gravel  base,  there  can  be  no  objection  to  it,  and 
it  certainly  forms  a  much  more  solid  and  compact  roadbed  than 
could  otherwise  be  obtained.  The  method  of  construction  of  tha 
road  proper  will  be  the  same  as  that  described  for  the  macadam 
pavement,  and  the  remarks  made  on  construction  there  can  be  ap- 
plied to  road  construction  with  full  force. 


BROKEN-STONE  PAVEMENTS.  361 


Quantity  of  Material. 

The  amount  of  stone  to  be  used  in  any  road-construction  will 
depend  upon  the  amount  of  rolling  and  consolidation  that  is  given 
to  it.  It  is  generally  conceded  by  the  best  authorities  that  ordinary 
broken  stone  as  used  upon  the  street  contains  about  45  per  cent 
voids.  If  we  assume  that  the  voids  are  compacted  under  the  roller 
to  20  per  cent  and  then  filled  with  binder,  the  shrinkage  caused 
by  the  rolling  will  be  the  same  as  the  reduction  of  voids,  or  25 
per  cent.  Consequently  it  will  require  10§  inches  of  loose  stone 
spread  upon  the  road  to  make  a  thickness  of  8  inches  when  con- 
solidated, and  about  2  inches  of  binder  will  be  required  to  fill  the 
voids. 

As  a  matter  of  fact,  however,  the  voids  are  probably  not  abso- 
lutely filled  by  the  binder,  as  the  stone  must  wear  into  the  base 
to  a  certain  extent,  so  that  with  the  above  amount  of  2  inches 
sufficient  will  be  left  to  cover  the  surface  of  the  road.  When  the 
road  is  finished  to  an  absolute  and  arbitrary  grade,  any  soft  place 
of  the  roadbed  is  liable  to  increase  the  amount  of  stone  required, 
as  any  loss  in  the  foundation  must  be  made  good  at  the  surface. 

To  construct  18,400  square  yards  of  macadam  previously  re- 
referred  to  under  "  Boiling  "  required  5400  yards  of  broken  stone 
and  900  cubic  yards  of  trap-rock  screenings.  This  would  give  an 
area  of  3.4  square  yards  of  finished  surface  to  1  cubic  yard  of  loose 
stone,  and  J  of  the  amount  for  binder.  This  piece  of  work  was 
conscientiously  and  carefully  done,  and  these  amounts  can  be  con- 
sidered a  fair  average  of  what  would  be  required  on  similar  work. 

In  a  discussion  on  road-making  before  the  American  Society 
of  Civil  Engineers,  previously  referred  to,  Mr.  W.  C.  Foster  in 
speaking  on  this  point  said  that  in  some  road-construction  carried 
on  under  his  direction  the  thickness  of  the  loose  stone  was  from 
5|  to  6  inches  on  4-inch  work,  and  from  7J  to  7-J  inches  on  6-,inch 
work,  and  adds  that  the  thicknesses  were  calculated  from  the  actual 
car  measurements  and  the  number  of  yards  laid.  These  results 
vary  a  little  from  that  already  given,  but  the  difference  is  probably 
no  more  than  would  generally  occur  on  roads  laid  on  an  earth  base. 


362        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


Cost  of  Construction. 

The  cost  of  building  a  macadam  road  is  governed  by  so  many 
different  conditions  that  the  cost  in  one  place  cannot  be  considered 
as  a  criterion  for  that  in  -another,  as  the  variations  are  quite  great 
when  apparently  the  conditions  are  the  same.  The  practice  in  New 
Jersey  is  to  have  the  work  done  for  a  contract  price  per  square  yard. 
According  to  the  report  for  1897  the  average  cost  of  two  roads  of 
10-inch  macadam  was  56  cents,  but  the  price  for  one  was  70  cents, 
and  for  the  other  43  cents.  The  average  cost  of  three  roads  8 
inches  thick  was  58  cents,  for  6-inch  roads  40  cents,  and  for  4-inch 
roads  32  cents  per  square  yard: 

Mr.  Henry  I.  Budd,  Eoad  Commissioner  of  New  Jersey,  stated 
before  the  American  Society  of  Civil  Engineers  that  under  the 
first  working  of  the  State  law  roads  cost  from  $7000  to  $10,000 
per  mile.  Afterwards  they  were  made  somewhat  thinner  and  the 
cost  was  reduced  to  from  $6000  to  $7000  per  mile.  In  1897  they 
cost  about  $5000  per  mile,  and  in  1898  $4000;  while  two  roads  10 
feet  wide  and  8  inches  deep  were  built  for  $3000  per  mile,  and  the 
cost  of  90  miles  being  constructed  at  that  time  (1898)  was  expected 
to  be  about  $4500  per  mile.  The  rock  in  many  instances  was  found 
adjoining  the  roads  themselves,  so  that  the  crushers  were  estab- 
lished practically  on  the  work,  where  the  haul  was  reduced  to  a 
minimum,  and  where  the  small  variations  in  the  thickness  of  the 
road  made  no  great  difference  in  the  cost. 

In  Massachusetts  the  practice  is  to  purchase  the  stone  by  the 
ton  and  then  have  the  work  carried  out  by  the  contractor.  The 
price  for  stone,  as  given  in  the  report  for  1898,  shows  a  variation 
in  cost  for  local  field-stone  of  from  $1  to  $2  per  cubic  yard,  and 
for  trap-rock  from  $1.20  to  $2.20  per  cubic  yard,  and  the  average 
cost  of  the  roads  built  in  that  State  is  given  at  about  $5700.  In 
a  table  given  in  the  latter  part  of  the  report  for  1898  the  cost  per 
standard  mile  of  road  15  feet  wide  is  given  for  all  roads,  contracted 
to  date  of  December  31,  1898,  in  the  different  towns  of  the  State. 
Those  for  macadam  with  surfacing  and  shaping  varied  from  about 
$3000  to  $9174  per  standard  mile. 

On  the  assumption  that  the  roadbed  and  base  have  already  been 


BROKEN-STONE  PA  VEMENT8.  363 

prepared,  the  cost  of  a  macadam  road  has  been  estimated  as  what 
might  be  expected  under  ordinary  conditions,  and  corrections  can 
easily  be  made  for  any  variations  that  may  occur: 

240  cubic  yards  of  stone  at  $1.50  per  yard $360.00 

40  cubic  yards  of  binding  material  at  $1.50. ...  60.00 

1  foreman  at  $3 3.00 

10  laborers  at  $1.50  per  day •. 15.00 

2  rollers  at  $10  per  day 20.00 

Sprinkling 10.00 

Total $468.00 

Assuming  that  one  cubic  yard  of  loose  stone  will  lay  3£  square 
yards  of  pavement  8  inches  thick,  and  that  one  roller  will  complete 
420  square  yards  per  day,  the  above  material  and  organization  will 
lay  840  square  yards  per  day  at  a  cost  of  56  cents  per  yard,  or  mak- 
ing as  the  itemized  cost  per  yard: 

Cents. 
Stone 43 

Binder 7 

Labor   2 

Sprinkling iy2 

Rolling 2y2 

Total 56 

Extracts  are  here  given  from  the  State  specifications  for  road- 
building  from  New  Jersey  and  New  York,  as  far  as  relates  to  the 
actual  work  of  road-construction.  There  are  also  given  the  speci- 
fications of  Mr.  Jas.  Owen  of  Newark,  N.  J.,  who  has  constructed 
so  many  miles  of  roads  in  that  State.  It  will  be  seen  that  he  uses 
as  a  binding  material  a  certain  amount  of  cjay,  which  is  contrary 
to  the  practice  of  nearly  all  of  the  road-builders  in  this  country. 
While,  in  the  light  of  Mr.  Owen's  results,  it  would  be  hardly  fair 
to  criticise  his  work,  this  practice  could  hardly  be  recommended  in 
general,  as  it  is  probable  that  the  good  results  obtained  by  Mr. 
Owen  have  been  on  account  of  the  peculiar  clay  in  New  Jersey  and 
the  engineer's. knowledge  of  the  way  to  use  it. 


364        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


New  York  Specifications. 

"  Kinds  and  Sizes  of  Broken  Stone. — The  broken  stone  shall  be 
of  two  courses.  The  bottom  course  will  be  four  inches  thick  after 
rolling  and  may  consist  of  gneiss,  granite,  flint,  or  any  of  the  harder 
grades  of  limestone,  broken  in  sizes  varying  from  one  and  one- 
quarter  inches  to  two  and  one-half  inches. 

"  The  top  course  will  be  two  inches  thick  after  rolling  and  will 
consist  of  trap-rock,  broken  in  sizes  varying  from  one-half  inch  to 
one  and  one-quarter  inches. 

"  Screenings  free  from  all  dirt  and  dust  shall  be  added  to  fill  all 
interstices  that  cannot  be  filled  by  the  rolling  or  compacting  of 
the  other  stone.  Such  screenings  will  be  of  the  same  class  of  stone 
as  the  course  into  which  they  are  to  be  rolled,  and  must  be  free 
from  earth,  sand,  loam,  vegetable  or  any  foreign  matter  and  contain 
as  small  a  percentage  of  dust  as  is  practicable. 

"  Spreading  and  Rolling. — After  the  earth  f oundaton  has  been 
completed  agreeably  to  these  specifications  and  has  passed  the  in- 
spection of  the  said  engineer,  a  layer  of  the  broken  stone  of  the 
quality  and  size  herein  specified  for  the  bottom  course,  and  of  such 
a  depth  as  will,  w'hen  rolled,  make  a  course  four  inches  thick,  shall 
be  spread  evenly  over  the  subgrade;  this  layer  is  then  to  be  rolled 
until  the  stone  is  as  closely  fitted  together  as  practicable,  with  or 
without  sprinkling  as  may  be  directed.  Such  an  amount  of  screen- 
ings as  can  be  introduced  without  separating  the  stone  is  to  be 
rolled  into  each  course  or  layer  so  as  to  fill  the  interstices^  and 
stone  is  to  be  added  or  removed  so  as  to  make  the  surface  practi- 
cally of  the  proper  height. 

"  The  next  overlying  course  will  be  of  stone  as  hereinbefore 
described  for  said  course,  and  is  to  be  spread  at  such  a  depth  that 
the  surface,  when  rolled,  will  be  at  the  proper  grade  irrespective 
of  the  finishing  material;  this  layer  is  then  to  be  rolled,  and  dur- 
ing the  process  of  rolling,  if  necessary,  similar  stone  is  to  be  added 
or  removed  from  time  to  time,  so  that  when  the  rolling  ceases  the 
roadway  is  truly  surfaced  to  the  required  grade  and  crown.  Dur- 
ing the  process  of  rolling  the  upper  course  of  stone,  screenings 
shall  be  introduced  dry,  in  such  manner  and  quantity  that  the 


BROKEN- STONE  PAVEMENTS.  365 

Interstices  shall  be  entirely  and  completely  filled  with  screenings; 
and  after  the  upper  layer  has  become  sufficiently  compact,  there 
shall  be  spread  upon  the  surface  sufficient  screenings,  as  specified, 
to  produce  a  smooth,  true  surface  when  rolled.  The  rolling  is  to 
-continue  until,  by  sufficient  use  of  water,  a  wave  is  produced  be- 
fore the  wheel  of  the  roller.  The  surface  of  any  course  shall  be 
scratched,  if  required,  so  as  to  obtain  the  proper  bond  with  that 
next  overlying. 

"  The  rolling  of  the  stone  and  screenings  shall  be  done  with  a 
steam-roller  weighing  not  less  than  ten  tons. 

"  Each  layer  of  the  broken  stone  and  the  screenings  shall  be 
well  and  thoroughly  rolled,  and  the  rolling  on  each  layer  shall 
be  prosecuted  until,  in  the  opinion  of  the  Engineer,  such  course 
shall  have  been  completed  as  hereinbefore  specified,  and  until  each 
layer  and  the  finished  surface  shall  be  rolled  and  finished  to  his 
entire  satisfaction  and  approval. 

"  The  amount  of  rolling  shall  not  be  less  than  100  times  over 
<?ach  square  yard  of  surface. 

"  During  the  rolling  of  the  lower  course  of  stone  only  so  much 
water  shall  be  sprinkled  thereon  as  is  necessary  to  prevent  wear- 
ing by  attrition;  but  in  rolling  the  upper  course  of  stone  and 
screenings,  water  is  to  be  applied  in  such  quantities  and  in  such 
manner  as  to  completely  and  compactly  fill  all  interstices  with 
screenings,  so  as  to  secure  a  "  set "  and  to  produce  the  wave  here- 
inbefore referred  to;  and  the  screenings  shall  be  worked  in  and 
through  to  further  this  result,  and  shall  be  applied  to  such  an  ex- 
tent as  is  necessary  for  puddling. 

"After  all  the  interstices  of  the  stone  are  filled  with  screen- 
ings, forty-eight  hours  may  elapse  before  the  final  puddling  if,  in 
1he  opinion  of  the  Engineer,  a  better  result  will  be  obtained 
thereby;  but  nothing  in  this  provision  shall  be  construed  as  en- 
titling the  Contractor  to  longer  time  in  completing  his  work 
according  to  the  terms  of  this  contract." 

New  Jersey  Specifications. 

"  4.  The  stone  construction,  if  of  telf ord,  to  be  made  of  a  bot- 
tom course  of  stone,  of  an  average  depth  of  not  more  than  five 


366        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

inches,  to  be  set  by  hand  as  a  close,  firm  pavement,  the  stones  to 
be  placed  on  their  broadest  edges  lengthwise  across  the  road  and 
so  as  to  break  joints  as  much  as  possible,  the  breadth  of  the  upper 
edge  not  to  exceed  four  inches.  The  interstices  are  then  to  be 
filled  with  stone  chips,  firmly  wedged  by  hand  with  hammer  and 
projecting  points  broken  off.  No  stone  to  be  used  of  a  greater 
length  than  ten  inches  or  width  of  four  inches,  except  each  alter- 
nate stone  on  outer  edge,  which  shall  be  double  the  length  of  the- 
others  and  well  tied  into  the  bed  of  the  road;  all  stone  with  a  nat^ 
smooth  surface  to  be  broken.  The  whole  surface  of  this  pave- 
ment to  be  subjected  to  a  thorough  settling  or  ramming  with 
heavy  sledge-hammers  and  thoroughly  rolled  with  a  five-  or  seven- 
ton  roller.  No  stones  larger  than  one-half  inch  to  be  left  loose 
on  top  of  telford. 

Broken  Stone. — "  5.  inches  of  broken  stone  are  to  be 

put  on  the  telford  foundation  to  a  depth  to  make  the  road  when 
finished  (including  binding  and  surface  finish)  -  -  inches;  to 
be  composed  of  one-and-one-quarter-inch  stone  which  will  pass 
through  a  ring  of  one  and  one-half  inches  in  diameter.  Said 
stones  to  be  as  nearly  cubical  as  possible;  to  be  evenly  and  thor- 
oughly compacted  by  rolling.  Any  inequalities  during  the  rolling 
are  to  be  carefully  filled  with  additional  material,  so  as  to  produce 
an  even  surface  on  this  and  the  following  macadam  construction. 

Macadam. — "  6.  If  of  macadam,  after  the  roadbed  has  been 
formed  and  rolled  as  above  specified,  and  has  passed  the  inspection 
of  the  Engineer  and  Supervisor,  the  first  layer  of  broken  stone^ 
consisting  of  inch-and-a-half  stone,  or  stone  that  will  pass  through 
a  ring  two  inches  in  diameter,  shall  be  deposited  in  a  uniform 

layer  having  a  depth  of  inches,  after  rolling,  and  rolled 

repeatedly  until  compacted  to  the  satisfaction  of  the  Engineer. 
The  second  course  of  broken  stone  shall  consist  of  inch-and-a- 
quarter  stone;  that  is^  every  piece  of  stone  shall  be  broken  so  that 
it  can  be  passed  through  a  ring  one  and  one-half  inches  in  diam- 
eter, and  no  stone  shall  be  more  than  two  inches  or  less  than  one- 
inch  long.  All  stone  must  be  as  nearly  cubical  as  possible,  broken 
with  the  most  approved  modern  stone-crushing  machinery,  free- 
from  screenings,  earth,  and  other  objectionable  substances,  and  in 
uniform  sizes.  This  course  is  to  be  spread  in  a  uniform  layer  to  a 


I 
BROKEN-STONE  PAVEMENTS.  367 

depth  of  at  least inches,  and  after  rolled  until  thoroughly 

settled  into  place  to  the  satisfaction  of  the  Supervisor,,  under  the 
instruction  of  the  Engineer. 

Binding  and  Finishing. — "  7.  The  surface  of  each  course  to  be 
thoroughly  and  repeatedly  rolled  and  sprinkled  until  it  becomes 
firm,  compact,  and  smooth.  When  the  two  courses  are  rolled  to 
the  satisfaction  of  the  Engineer,  a  coat  of  three-quarter-inch 
stone  and  screenings  is  to  be  spread  of  sufficient  thickness  to  make 
a  smooth  and  uniform  surface  to  the  road,  then  again  thoroughly 
rolled  until  the  road  becomes  thoroughly  consolidated,  hard,  and 
smooth,  and  a  small  stone  placed  on  the  surface  will  be  broken 
before  being  driven  into  the  bed.  Rolling  to  be  done  by  Con- 
tractor, with  a  ten-ton  steam-roller  approved  by  the  Engineer.  If 
the  conditions  are  such  that  a  roller  of  less  weight  would  be  more 
efficient,  the  Engineer  and  Supervisor  may  require  the  use  of  the 
same.  Any  depressions  formed  during  the  rolling  or  from  any 
other  cause  are  to  be  filled  with  three-quarter-inch  stone  and 
screenings,  and  the  roadway  brought  to  a  proper  grade  and  curva- 
ture as  determined  by  the  Engineer.  Water  must  be  applied  in 
such  quantities  and  in  such  manner  as  to  completely  fill  all  voids 
between  the  broken  stone,  with  the  binding  material  saturated  so 
as  to  secure  a  set. 

Manner  of  Rolling. — "  8.  In  the  rolling  the  roller  must  start 
from  the  side  lines  of  the  stone  bed  and  work  towards  the  centre, 
unless  otherwise  directed.  The  rolling  shall  at  all  times  be  subject 
to  the  direction  of  the  Engineer  and  Supervisor,  who  may,  from 
time  to  time,  direct  such  methods  of  procedure  as  in  their  opinion 
the  necessities  of  the  case  may  require. 

Material. — "  9.  The  stone  for  the  construction  of  this  road 
is  to  be  of  the  same  kind  and  quality,  or  equally  as  good,  in  every 
particular,  as  that  shown  in  the  Engineer's  office.  The  stone  used 
for  telford  foundation-course  must  be  of  hard,  durable  nature,  not 
liable  to  disintegrate  by  frost  or  weather;  for  macadam  foundation 
course  must  be  of  the  best  trap-rock.  The  inch-and-a-quarter 
and  three-quarter-inch  stone,  and  screenings  for  the  final  finish, 
must  be  of  the  best  Jersey  trap-rock/' 


668        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


Mr.  Owen's  Specifications. 

"  Foundation  to  be  of  stone,  six  inches  deep,  to  be  set  by  hand 
in  the  form  of  a  close  pavement;  the  stones  to  be  laid  with  their 
largest  side  down  in  parallel  rows  across  the  street,  the  joints  to 
break  .as  much  as  possible.  The  breadth  of  the  upper  edge  of  stones 
not  to  exceed  eight  inches  and  not  less  than  four  inches.  The 
interstices  are  then  to  be  filled  with  stone  chips  firmly  wedged  by 
hand  with  a  hammer  and  the  projecting  points  broken  off,  and  the 
whole  surface  to  be  subjected  to  a  thorough  settling  or  ramming 
with  a  heavy  sledge-hammer. 

"  On  top«of  the  foundation  a  course  of  broken  stone  not  larger 
than  two  inches  in  diameter  is  to  be  laid,  spread,  and  thoroughly 
rolled.  Sufficient  stone  is  to  be  spread  to  make  a  depth  of  two 
inches  when  consolidated. 

"  Good  loam  or  clay  is  to  be  placed  in  a  thin  layer  on  top  of 
the  two-inch  stone  and  thoroughly  rolled.  Only  sufficient  packing 
is  to  be  used  as  is  necessary  to  bind  the  stone  and  according  to 
instructions.  On  top  of  the  two-inch  stone  a  course  of  broken  stone 
not  larger  than  one  and  one-half  inches  in  diameter  and  not  less 
than  one  inch  in  diameter  is  to  be  spread  and  thoroughly  rolled. 
Sufficient  stone  is  to  be  spread  to  make  a  depth  of  two  inches  when 
consolidated.  On  top  of  this  course  spread  another  layer  of  pack- 
ing similar  to  the  first  course. 

"  When  the  broken  stone  is  thoroughly  rolled  and  consolidated, 
a  coat  of  screenings  is  to  be  spread  of  sufficient  thickness  to  make 
a  uniform  surface  to  the  road  when  rolled. 

"  All  stone  to  be  of  Orange  Mountain  trap-rock,  or  trap-rock 
of  equal  quality,  subject  to  the  approval  of  the  Road  Committee 
and  Engineer." 

Maintenance  of  Eoads. 

No  matter  how  well  constructed,  or  of  what  material,  a  mac- 
adam road  will  require  constant  care  in  order  to  be  kept  in  good 
condition.  There  are  two  methods  in  common  use — one  to  supply 
the  waste  on  account  of  traffic  gradually  as  it  is  worn  off,  and  so 
maintain  the  full  thickness  of  the  road;  the  other  by  keeping 


. 

BROKEN-STONE  PAVEMENTS.  369 

the  surface  in  good  condition,  and  when  it  has  become  worn  thin, 
resurface  it  entirely.  Both  methods  have  their  advocates,  and 
it  is  probable  that  each  is  better  under  certain  conditions.  The 
wear  of  macadam  road  is  caused  both  by  traffic  and  the  action  of 
the  weather.  The  latter  is  continuous,  while  the  former  is  inter- 
mittent. The  action  of  the  weather  depends  upon  the  action  of  the 
frost,  which  must  be  guarded  against  by  drainage,  and  washing  of 
surface-water,  and  this  must  be  provided  for  by  proper  construc- 
tion. 

It  seems  to  be  generally  conceded  by  engineers  who  have  studied 
this  part  of  the  subject  that  the  action  of  the  horses'  feet  does 
more  damage  to  the  macadam  road  than  does  the  action  of  the 
wheels.  The  former  serves  to  pick  up  and  loosen  the  individual 
stones,  while  the  latter,  while  wearing  them  to  a  certain  extent, 
serves  to  keep  them  solid  and  compact. 

Sir  J.  MacXeill  in  some  evidence  given  before  a  Parliamentary 
Committee,  according  to  Codrington,  stated  that  of  the  total  wear 
of  a  road  80  per  cent  of  the  average  was  due  to  traffic  and  20  per 
cent  to  atmospheric  causes,  and  of  the  80  per  cent  due  to  traffic 
60  per  cent  was  due  to  the  wear  of  the  horses's  feet  and  20  per  cent 
to  the  wheels  in  the  case  of  fast  coaches,  and  44£  per  cent  to  the 
horses'  feet  and  35|  per  cent  to  the  wheels  in  the  case  of  wagons. 

The  actual  amount  of  wear  to  the  road  must  depend  practically 
upon  the  amount  of  traffic,  and  also  upon  the  character  of  the 
material  and  method  of  construction.  In  any  case,  the  amount 
of  wear  of  one  road  would  serve  as  a  poor  guide  for  a  standard 
for  another,  without  equating  for  traffic,  character  of  material, 
and  method  of  construction.  The  records  of  amount  of  material 
used  on  different  roads,  however,  are  of  a  certain  amount 
of  value.  Codrington  gives  110  cubic  yards  of  material  per  mile 
per  annum  on  235  miles  of  turnpike  road  in  Glamorganshire,  Wales. 
In  Carmarthenshire  the  average  of  290  miles  of  road  during  ten 
years  was  73  cubic  yards  per  mile  per  year.  In  Pembrokeshire  the 
average  of  85  miles  of  turnpike  road  was  64  cubic  yards  per  mile, 
while  in  other  sections  the  amount  ranged  from  48  to  58  cubic  yards 
per  mile. 

Mr.-  W.  Hewett,  in  a  paper  read  before  the  Surveyors'  Institution 
of  Great  Britain,  November  26,  1888,  said:  "  The  amount  of  ma- 


370        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

terial  expended  annually  in  this  country  on  main  roads  varies  from 
about  40  cubic  yards  per  mile  in  remote  country  districts  to  1000 
and  sometimes  1500  cubic  yards  in  the  vicinity  of  large  towns; 
but  I  think  the  general  average  would  be  from  70  to  80  cubic 
yards  per  mile.  On  district  and  parish  roads  it  is  frequently  as 
low  as  10  cubic  yards  per  mile. 

Kockwell,  in  his  book  on  "  Koads  and  Pavements  in  France," 
gives  49  cubic  yards  as  the  average  amount  per  mile  used  on  2209 
miles  of  routes  nationales  for  the  year  1893.  He  also  says  that  on 
these  roads  measurements  are  taken  at  different  periods  to  ascer- 
tain whether  the  roadway  has  been  fully  maintained  by  the  amount 
of  material  added  annually.  The  average  of  about  500,000  tests 
made  in  1891  showed  a  thickness  of  5-J  inches,  which  was  only 
•£%  of  an  inch  less  than  the  thickness  determined  in  1886,  thus 
showing  that  the  general  thickness  of  the  road  was  practically 
maintained.  The  State  Engineer  of  New  York,  in  a  bulletin  issued 
in  October,  1899,  says  that  a  road  16  feet  wide  would  probably 
require  about  32  cubic  yards  of  material  each  year  to  keep  it  in 
good  condition. 

The  cost  of  these  repairs  would  depend  upon  the  existing  con- 
ditions. As  showing  how  much  these  sometimes  amount  to.  in 
money,  Mr.  G.  J.  Crosby  Dawson  in  a  work  published  in  1876  says 
that  £280,000  were  annually  spent  on  the  macadam  streets  and 
roads  of  London,  and  £4,000,000  on  the  turnpike  roads  and  high- 
ways of  England  and  Wales. 

Probably  the  macadam  streets  of  London  have  cost  more  for 
maintenance  on  account  of  their  heavy  traffic  than  those  of  other 
cities.  It  is  said  that  in  1884  Parliament  Street  cost  70  cents,. 
Whitehall  Street  71  cents,  and  Victoria  Street  50  cents  per  square 
yard  for  maintenance  only. 

Paris  in  1893  expended  44  cents  per  square  yard  for  main- 
tenance of  her  macadam  streets. 

Maintenance  of  the  macadam  streets  of  Glasgow,  Scotland,  in 
1896  and  1897  cost  about  12  cents  per  yard.  The  cost  of  the 
Massachusetts  roads  for  maintenance,  according  to  the  report  of 
1898,  was  about  $108  per  mile,  including  general  repairs  to  the 
roads,  such  as  washouts,  etc.,  exclusive  of  the  macadam  roadway. 

The  cost  in  France  in  1876  for  the  national  highways  was 


. 

BROKEN-STONE  PAVEMENTS.  371 

$165  per  mile.  The  following  figures  give  the  prices  per  square 
yard  for  maintenance  of  macadam  roads  in  different  cities  and 
countries  of  Europe: 

Cents. 

LiSge,   Belgium 1*4 

Marseilles  averaged Ql/2 

Heavy-traffic  streets 33 

Dresden    3% 

Edinburgh 6 

Tuscany 3  to  4 

Spain 3 

Switzerland 3 

Resurfacing  macadam  streets  in  Rochester,  N.  Y.,  cost  7  cents 
per  square  yard  in  1898. 

Huts. 

Probably  one  of  the  worst  features  of  the  wear  of  macadam 
roads,  and  the  hardest  for  the  engineer  to  overcome,  is  the  for- 
mation of  ruts.  This  should  be  prevented  if  possible  by  spreading 
the  traffic  as  much  as  possible  over  the  surface  of  the  road,  and  by 
having  the  tires  of  the  vehicles  of  such  width  as  will  sustain  the 
load  without  damage.  Ruts,  however,  will  sometimes  form,  es- 
pecially when  a  large  amount  of  heavy  material  is  carried  over  a 
road  in  a  short  time,  the  teams  regularly  following  each  other  and 
the  wheels  running  in  the  same  place  naturally  after  the  rut  has 
begun  to  form. 

In  treating  these  ruts,  the  road  should  be  picked  up  to  a  suffi- 
cient width  and  depth,  so  that  when  new  material  is  added  it  will 
form  a  part  of  the  old  and  not  be  simply  new  material  superim- 
posed upon  the  old.  Otherwise  the  ruts  are  liable  to  be  formed 
again,  as  the  new  material,  under  such  conditions,  will  wear  more 
rapidly  than  when  it  forms  a  part  of  the  entire  road.  This  mate- 
rial also  should  be  of  the  same  character  as  that  already  used. 
Otherwise  the  wear  will  become  unequal  and  the  road  become 
.abnormally  rough  and  uneven. 


372        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


Sprinkling. 

The  proper  maintenance  of  macadam  roads  or  paved  streets 
involves  systematic  sprinkling.  This  serves  a  double  purpose.  It 
prevents  the  material  from  blowing  away  whenever  small  parts  of 
it  are  loosened.  The  loose  material  on  a  street  when  sprinkled 
serves  as  a  cushion  for  the  wheels  of  the  vehicles,  and  thus  pre- 
vents to  a  great  extent  the  direct  action  on  the  stone,  thereby 
saving  a  large  amount  of  wear.  It  also  prevents  the  surface  from 
picking  up  or  ravelling  under  traffic  in  the  dry  season  and  so  pre- 
vents abnormal  wear.  It  is  generally  conceded  by  engineers  that 
judicious  sprinkling  on  a  macadam  road  will  more  than  pay  for 
itself  in  the  increased  life  it  gives  to  the  road,  without  takjng  into 
consideration  the  prevention  of  dust.  Sprinkling,  however,  should 
be  done  with  care  and  intelligence.  It  should  be  done  often  rather 
than  have  a  large  amount  of  water  applied  at  one  time,  the  object 
being  to  keep  the  loose  material  on  top  damp  rather  than  wet,  so 
as  to  prevent  the  formation  of  mud,  or  washing  of  the  material 
into  the  gutter  if  the  water  is  applied  in  large  quantities. 

Broad  Tires. 

The  width  of  tires  on  heavy-traffic  vehicles  has  a  great  bearing- 
upon  the  wear  of  macadam  roads.  Loads  borne  by  wheels  with 
narrow  tires  often  prove  very  detrimental  and  even  destructive  to 
macadam  roads,  when  the  same  loads  sustained  by  broad  tires 
would  cause  no  abnormal  wear,  and  might  even  in  some  cases  be- 
beneficial. 

This  point  has  received  some  attention  by  the  legislators  of 
this  country,  but  more  in  Europe,  where  laws  have  been  enacted 
regulating  the  width  of  tires  on  vehicles  carrying  heavy  loads. 

According  to  figures  given  in  Table  No.  48  it  would  seem  that 
on  ordinary  roads  there  is  not  much  difference  in  the  force  re- 
quired to  draw  loads  on  wheels  of  different  width  of  tires,  but  the- 
action  of  the  wheels  upon  the  roads  is  very  different. 

New  Jersey. — In  New  Jersey  the  Legislature  of  1897  passed  a 
law  governing  the  width  of  tires,  which  was  vetoed  by  the  Gov- 
ernor simply  because  it  applied  to  cities  as  well  as  rural  districts. 


BROKEN-STONE  PAVEMENTS.  373 

This  law  provided  that  a  rebate  of  taxes  for  road  purposes 
should  be  allowed  to  the  owners  of  all  vehicles  having  tires  of  not 
less  than  3J  inches  in  width  used  for  transporting  heavy  loads 
drawn  by  two  or  more  horses;  the  rebate  amounting  to  three  dol~ 
lars  for  each  wheel  in  habitual  use.  Also,  that  the  owner  of  each 
vehicle  having  tires  of  not  less  than  4  inches  in  width  upon  which 
there  is  a  difference  of  at  least  8  inches  in  the  length  of  the  front 
and  rear  axles,  so  constituted  that  the  front  and  rear  wheels  should 
not  come  into  contact  with  the  same  road  surface,  should  receive  a 
further  rebate  of  four  dollars  per  year  for  each  of  such  vehicles  in 
habitual  use;  and  also  that  each  vehicle  used  for  transporting 
heavy  loads  drawn  by  two  horses  should  be  assessed  fifty  cents  per 
annum  for  every  wheel  having  a  less  width  than  3J  inches. 

Rhode  Island. — An  act  passed  by  the  Legislature  of  Rhode 
Island  in  1897  regulated  the  width  of  tires  according  to  the  size 
of  the  axles  as  follows: 

Size  of  Axle.                            Minimum  Width  of  Tire. 
If  inches If  inches. 

U     "     ...  U 

If,  U  inches 2± 

1|,  2,  2i  inches 3± 

2i,  2f ,  2±,  2|  inches 4 

2i,  2|,  3  "       5 

Larger  than  3    "       6 

It  also  provided  that  all  wheels  built  or  new-rimmed  after 
April  1,  1898,  should  be  provided  with  tires  in  accordance  with 
the  above. 

This  Act  did  not  apply  to  the  apparatus  of  fire  departments,  to 
vehicles  used  on  iron  tramways,  nor  to  carriages  with  rubber  tires. 

A  bill  very  similar  to  the  above  was  introduced  in  the  Legisla- 
ture of  1900.  It  provides  that  the  rebate  should  be  two  dollars  for 
each  wheel  with  tires  4  inches  in  width  in  habitual  use  as  above  oil 
April  1,  1901,  and  one  dollar  for  each  similar  wheel  for  1902.  In 
other  respects  it  was  like  the  bill  of  1897. 

Michigan. — A  Michigan  statute  provides  that  all  persons  who 
shall  have  used  only  lumber  wagons  on  the  public  highways  of  the 
State  with  rims  not  less  than  3£  inches  in  width  for  hauling  loads 
exceeding  800  pounds  in  weight  shall  receive  a  rebate  of 


374        STREET  PAVEMENTS  AND  PA  VINO  MATERIALS. 

fourth  their  assessed  highway  taxes,  provided  that  no  rebate  shall 
exceed  three  days'  road-tax  for  any  person. 

New  York. — Statutory  provision  is  made  that  a  rebate  of  one- 
half  of  his  assessed  highway  tax  shall  be  made  each  year  to  each 
person  who  uses  on  public  highways  wagons  or  vehicles  upon  which 
two  or  more  horses  are  used,  having  wheels  the  tires  of  which  shall 
not  be  less  than  three  inches  wide;  not  to  exceed,  however,  four 
dollars  or  four  days'  labor.  Also,  that  in  the  counties  where  the 
aggregate  sum  expended  for  macadamizing  or  paving  public  roads 
exceeds  the  sum  of  five  hundred  thousand  dollars  the  Board  of 
Supervisors  shall  have  power  to  regulate  the  width  of  tires  for 
Vehicles  built  to  carry  a  load  of  2500  pounds  or  more. 

In  accordance  with  the  above  the  Supervisors  of  Queens  County 
passed  an  ordinance  requiring  all  such  wagons  to  have  tires  not 
less  than  3  inches  in  width. 

Ohio. — In  Ohio  it  is  made  unlawful  for  any  persons  to  transport 
over  macadamized,  gravel,  or  stone  roads  loads  of  more  than  two 
thousand  pounds  in  vehicles  having  wheels  with  tires  less  than 
3  inches  in  width,  and  authority  is  given  to  county  commis- 
sioners to  prescribe  the  width  of  tires  for  heavier  loads. 

In  counties  having,  according  to  the  census  of  1880,  a  popula- 
tion of  more  than  33,510  and  less  than  33,515  the  following  loads 
and  tire  widths  are  established: 

Loads,  Pounds.  Width  of  Tires. 

2,500  to  3,500 Not  less  than  3  inches. 

'     3,500  to  4,000 "       "        "       31/2    " 

4,000  to  6,000 "       "        "       4        " 

6,000  to  8,000 "       "        "       5 

8,000  and  over "      "       "      6       « 

Vermont. 

3  tons  to  4  tons Not  less  than  3  inches. 

4  tons  or  more "       "        "       4 

Pennsylvania. — An  artificial  road  between  Philadelphia  and  the 
Borough  of  Lancaster: 

2y2  to  3  tons Not  less  than  4  inches. 

3  to  3y2      "    "      "       "      7       " 

5  to  5y2      "    "      "       "     10       " 


BROKEN-STONE  PAVEMENTS.  375 

For  two-wheeled  vehicles  the  regulation  was: 

1%  to  iy2  tons Not  less  than  4  inches. 

2y8  to  3          "    "       "        "       7        " 

3y2  to  4          "    "       "        "10        " 

Indiana. — Indiana  has  a  law  prohibiting  the  hauling  on  a  wet 
gravel  road  of  a  load  of  over  2000  pounds  on  a  narrow-tired  and 
over  2500  pounds  on  a  broad-tired  wagon. 

Kentucky. — On  the  Kentucky  toll-roads  the  rates  are  regulated 
according  to  width  of  tires  as  follows: 

Cents. 

Narrow-tired  wagon  drawn  by  four  animals 40 

Four-inch-tired  wagon    "        "       "  "       35 

Narrow-tired  wagon       "        "     five         "       60 

Four-inch-tired  wagon   "        "      "  "       50 

Narrow-tired  wagon        "        "     six          "       75 

Four-inch-tired  wagon    "        "      "  "       60 

Foreign  Countries. 

Austria. — All  wagons  built  for  loads  of  more  than  2J  tons  must 
have  tires  at  least  4^  inches  wide  in  Syria  and  Corinthia.  For  from 
3J  to  4£  tons  the  tires  must  be  6£  inches  wide.  In  lower  Austria 
and  Bohemia  the  width  must  be  at  least  4|  inches  for  loaded 
wagons  drawn  by  two  or  three  horses. 

France. — The  tires  of  the  French  market-cart  vary  from  3  to  10 
inches  in  width,  being  generally  from  4  to  6  inches,  with  the  rear 
axle  about  14  inches  longer  than  the  forward  one. 

Germany. — The  law  provides  that  wagons  for  heavy  loads  shall 
have  flat  tires  at  least  4  inches  wide,  and  light  vehicles  a  width  of 
at  least  2£  inches. 

Switzerland. — Wagons  must  be  provided  with  wheels  having 
tires  of  a  width  proportional  to  the  loads.  Wagons  drawn  by  two 
or  more  horses  shall  have  a  width  of  tire  not  less  than  one  inch  for 
each  draft-animal.  Vehicles  for  hauling  heavy  objects  that  cannot 
be  taken  apart  must  have  tires  at  least  6  inches  wide. 


CHAPTER  XII. 

PLANS    AND    SPECIFICATIONS. 

Purpose  of  Plans  and  Specifications. 

DETAILED  information  concerning  any  proposed  work  is  gen- 
erally furnished  by  means  of  plans  and  specifications,  the  latter 
showing  the  manner  in  which  the  work  is  to  be  carried  out,  and  the 
former  its  location  and  extent,  as  well  as  certain  details  in  the 
method  of  construction  that  cannot  easily  be  described  in  the- 
specifications.  Generally  speaking,  the  plans  should  be  made  first,, 
showing  exactly  where  the  work  is  situated,  its  bounding  limits  in 
each  direction,  and  all  details  necessary  for  a  thorough  knowledge 
of  what  is  to  be  done.  With  the  plans  before  him,  the  engineer 
is  prepared  to  describe  fully  the  method  of  construction.  Care- 
ful study,  however,  is  necessary  so  that  he  may  thoroughly  under- 
stand what  is  desired  and  be  able  to  make  plain  to  any  prospective- 
bidder  just  what  will  be  required.  He  should  be  careful  to  see  that 
there  is  no  conflict  between  the  plans  and  specifications,  as  this 
necessarily  brings  confusion  and  uncertainty  as  to  what  is  expected. 
Specifications. 

The  specifications  should  be  concise  and  explicit,  being  very 
careful  to  make  clear  exactly  what  is  to  be  done.  As  a  rule,  both 
the  corporation  and  the  contractor  will  be  better  served  by  having 
this  plainly  understood.  The  object  of  the  contractor  is  to  make 
money;  and  if,  by  some  trick  or  obscure  wording  of  the  specifica- 
tions, something  is  hidden  which  he  will  afterwards  be  called  upon 
to  perform,  he  will  be  disposed  to  slight  other  parts  of  the  work 
so  that  he  may  make  up  on  one  thing  what  he  loses  on  another. 
Specifications,  however,  should  not  be  too  full,  else  there  is  a  lia- 
bility to  conflict.  An  attempt  to  make  anything  too  plain  often 
results  in  creating  confusion  rather  than  clearness.  An  example 

376 


PLANS  AND  SPECIFICATIONS.  377 

of  this  was  shown  in  a  contract  which,  in  its  bidding  blank,  re- 
quired that  the  contractor  should  preserve  and  protect  all  street 
railways  from  any  damage.  In  one  section  the  specifications  pro- 
vided that  the  contractor  should  allow  the  owners  of  all  street 
railways  every  facility  for  shoring  up  and  protecting  their  tracks. 
This  was  plainly  a  conflict;  and  when  a  test  case  arose,  a  com- 
promise was  effected  by  which  the  city  paid  a  material  proportion 
of  the  extra  expense  caused  by  the  railway  tracks;  the  railway  com- 
panies holding  that  the  city  could  make  no  contract  that  would  be 
binding  upon  them,  and  the  contractor  maintaining  that  if  it 
was  his  duty  to  provide  the  street-car  company  with  facilities  for 
doing  their  work,  it  was  not  incumbent  upon  him  to  perform  U. 
If  the  engineer  who  drew  the  specifications  had  been  content  with 
the  first  clause  providing  for  the  contractor  to  do  all  work  on  the 
street-car  tracks  at  his  own  expense,  there  would  have  been  no 
trouble,  but  his  very  attempt  to  make  the  matter  more  binding 
really  released  the  contractor  from  his  obligation. 

The  engineer,  too,  should  understand  that  it  is  as  much  his 
province  to  have  work  done  well  at  its  lowest  possible  price  as  it 
is  to  have  the  work  well  done.  By  that  is  meant  that  he  should 
thoroughly  study  the  requirements  of  each  case  and  have  such 
knowledge  of  the  materials  to  be  used  that  he  should  not  ask  for 
anything  more  than  is  necessary.  In  other  words,  he  should  im- 
pose no  extra  cost  of  construction  upon  the  city  or  his  client  in 
order  simply  to  protect  himself. 
Contractors  to  Furnish  Plans. 

It  is  customary  on  some  classes  of  work  to  make  up  a  set  of 
general  specifications  and  ask  the  contractors  to  furnish  their  own 
plans.  As  a  whole  this  is  objectionable,  and  it  is  doubtful  if  a 
contract 'made  under  such  specifications  would  be  legal  under  a 
law  which  required  all  contracts  to  be  awarded  to  the  lowest 
responsible  bidder.  All  plans  and  specifications  should  be  so  made 
as  to  allow  the  greatest  competition,  for  when  one  contractor  bids 
upon  one  set  of  plans  and  another  upon  a  different  set,  the  result 
is  not  one  of  competitive  bidding. 

In  general  work,  however,  where  a  commission  or  board  has 
the  power  to  make  contracts  in  their  discretion,  and  where  the 
work  is  of  such  character  as  to  require  a  special  expert,  or  where 
the  exercise  of  superior  knowledge  or  ingenuity  would  arrive  at 


378        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

the  same  result  with  less  cost,  it  might  be  advisable  to  allow  the 
contractors  to  prepare  their  own  plans.  This  necessitates,  how- 
ever, a  careful  examination  of  all  plans  by  an  engineer  who  is 
thoroughly  conversant  with  the  matter  and  who  is  capable  of  giv- 
ing an  intelligent  and  unbiassed  opinion  as  to  the  most  desirable 
plan.  It  must  be  remembered  that  in  every  case  it  is  results  that 
are  looked  for,  and  that  it  is  proper  to  use  every  legitimate  method 
to  obtain  the  best  results  at  the  lowest  expense.  Contractors  and 
bidders,  however,  have  their  rights,  and  it  is  not  fair  or  honest  for 
any  corporation  to  call  for  bids  or  plans  unless  it  is  the  intention 
to  accept  the  one  that  is  deemed  the  most  favorable  to  the  inter- 
ests of  the  party  calling  for  bids. 
Clauses  to  be  En-forced. 

The  engineer  should  not  insert  any  clauses  in  the  specifications 
that  are  not  intended  to  be  enforced.  Otherwise  he  may  unneces- 
sarily increase  the  cost  of  the  work,  or  the  contract  will  be  drawn 
in  such  a  way  that  one  contractor,  knowing  the  custom  of  the 
locality  and  that  certain  provisions  are  not  intended  to  be  en- 
forced, will  bid  lower,  and  be  able  to  do  the  work  for  a  less  price, 
than  the  contractor  who  bids  simply  upon  the  exact  meaning  of 
the  specifications.  All  honest  contractors  wish  specifications  en- 
forced, for  then  they  know  just  how  to  make  their  figures,  just 
what  work  will  be  required  of  them,  and  feel  that  they  stand  upon 
an  equal  footing  with  other  bidders.  This  is  especially  neces- 
sary in  large  works  where  bids  are  asked  for  from  outside  parties. 
Description  of  Subsurface  Material. 

In  preparing  plans  for  work,  especially  that  which  requires  any 
subsurface  construction,  it  is  always  a  question  as  to  how  much 
information  should  be  given  or  advertised  as  to  the  character  of 
the  underground  material.  Some  cities  make  a  very  thorough  ex- 
amination in  such  cases,  and  on  their  plans  show  the  result  of 
their  examination — whether  water  or  rock  exists,  and  to  what 
extent.  It  has  always  seemed  that  this  was  a  rather  dangerous 
proceeding,  especially  in  the  case  of  water,  which  it  is  difficult  to 
pay  for  separately.  Where  rock  is  encountered  in  excavation  a 
special  price  is  generally  made  for  paying  for  it  by  the  cubic  yard. 
In  the  case  of  water  it  is  different;  and  it  would  seem  only  fair 
that  if  the  city  or  corporation  should  show  water  as  existing  in  a 
certain  part  of  the  work,  and  insert  the  requirement  in  the  specifi- 


PLANS  AND  SPECIFICATIONS.  379> 

cations  that  all  water  encountered  should  be  taken  care  of  by  the 
contractor  at  his  own  expense,  if  water  should  be  discovered  in 
other  parts  of  the  work  the  contractor  would  be  entitled  to  the 
extra  cost  of  doing  the  work  on  account  of  the  existence  of  the 
water.  This  would  be  a  matter  very  hard  for  the  engineer  in 
charge  of  the  work  to  adjudicate,  and  would  almost  always  result 
in  litigation. 

When  a  contractor  prepares  to  bid  upon  any  piece  of  work, 
he  expects  to,  and  it  only  seems  fair  that  he  should,  take  such 
steps  as  will  give  him  all  the  necessary  information  about  the 
character  of  the  material  to  be  encountered  as  will  enable  him  to 
put  in  an  intelligent  and  reasonable  bid.  Lf  the  corporation  re- 
quiring the  work  to  be  done  furnishes  all  information  as  to  where 
and  how  it  is  to  be  constructed,  that  would  seem  to  be  sufficient  in 
most  cases.  In  some  special  instances,  however,  where  the  work 
was  of  a  particularly  difficult  nature,  requiring  a  great  deal  of  pre- 
liminary work  before  any  knowledge  of  the  material  could  be 
obtained,  it  might  be  advisable  and  economical  to  all  concerned 
for  the  corporation  to  furnish  all  necessary  information.  It  must 
be  understood,  of  course,  that  if  the  contractor  makes  a  large  out- 
lay in  a  preliminary  investigation,  it  will  be  added  to  his  bid,  and 
the  party  for  whom  the  work  is  to  be  done  will  in  the  end  pay 
for  it. 
Quantity  of  Work  to  be  Done. 

With  the  plans  and  specifications  for  street  work,  and  in  fact 
for  nearly  all  kinds  of  work,  should  go  a  statement  giving,  as 
nearly  as  can  be  determined  in  advance,  the  exact  quantity  of 
work  to  be  performed.  By  this  is  not  meant  the  amount  of  mate- 
rial required  in  any  construction,  but  simply  the  aggregate  quan- 
tities of  the  different  parts  of  the  work.  This  should  be  obtained 
from  a  careful  survey,  and  a  price  called  for  in  the  bidding  blanks 
for  each  item  on  the  list.  This  method  shows  to  the  contractor 
the  amount  of  work  required  of  him,  and  it  also  enables  the 
engineer  to  determine  with  certainty  the  lowest  bidder,  and  to 
ascertain  whether  the  bid  is  made  out  intelligently  with  a  proper 
price  for  each  item. 
Lump  Sum  Bids. 

Some  people,  however,  advocate  the  letting  of  contracts  for  a 
lump  sum,  on  the  ground  that  the  contractor  in  looking  over  the 


380        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

work  will  be  apt  to  omit  or  forget  something  and  consequently  put 
in  a  bid  for  a  less  amount  than  he  otherwise  would.  That  is,  the 
intention  is  to  get,  if  possible,  a  certain  amount  of  work  done  for 
nothing.  This  is  neither  honest  nor  expedient,  because,  as  was 
said  before,  where  a  contractor  loses  on  one  part  of  the  work  he 
is  very  apt  to  make  good  his  loss  on  another.  It  is  exceedingly 
difficult,  however  close  and  intelligent  the  inspection,  to  watch 
the  contractor  at  all  times,  and  if  by  the  use  of  sharp  practice  on 
the  part  of  the  corporation  or  individual  he  has  been  led  into 
making  a  contract  by  which  he  will  lose  money,  it  is  not  to  be  won- 
dered at  that  he  will  attempt  to  recoup  himself  at  the  expense  of 
some  portion  of  the  work. 

No  individual  or  corporation  can  afford  to  have  work  done  for 
nothing.     Good  work  is  worth  a  good  price,  and  the  information 
placed  before  the  bidder  should  be  of  such  nature  that  he  can 
plainly  know  everything  that  will  be  required  of  him. 
Indeterminate  Quantities. 

It  often  happens  that  the  quantity  of  certain  parts  of  the  work 
cannot  be  determined  in  advance.  If,  however,  a  price  is  asked  for 
each  one  of  these  items,  a  quantity  must  be  fixed  in  order  to  deter- 
mine the  lowest  bidder  in  canvassing  the  bids;  but  if  this  quantity 
be  too  small  or  too  great,  this  difference,  when  the  bidding  is  close, 
may  make  a  difference  in  the  lowest  bid.  Then,  too,  when  the 
quantities  are  small,  the  contractors  are  apt  to  specify  a  large  price, 
as  the  sum  total  will  not  much  change  the  entire  bid.  To  avoid 
trouble  of  this  kind,  especially  where  work  is  not  to  be  paid  for 
by  assessment,  a  good  plan  is  for  the  engineer  to  determine  upon 
and  fix  in  the  specifications  a  price  that  will  be  paid  per  unit  for 
each  of  these  indeterminate  quantities.  It  has  been  decided  by  legal 
authorities  that,  even  if  work  were  to  be  paid  by  special  assess- 
ment and  as  the  result  of  competitive  bidding,  where  it  was  not 
possible  to  determine  accurately  the  amount  of  different  kinds  of 
work  called  for,  it  would  be  legal  to  specify  their  price  in  ad- 
vance, the  theory  being  that  there  would  be  less  liability  to  in- 
justice with  a  fair  price  specified  than  to  allow  the  contractors  to 
bid  on  an  uncertainty. 
Extra  Work. 

Another  thing  that  always  causes  much  trouble  in  all  contracts 
is  extra  work  and  claims  for  extra  work.    While  it  often  seems  im- 


f 

PLANS  AND  SPECIFICATIONS.  381 

possible  to  provide  beforehand  for  everything  that  will  be  re- 
quired, in  most  cases  it  can  be  done,  and  certainly  always  should 
be  if  possible.  Contractors  should  always  be  discouraged  from 
making  any  application  for  extras.  Specifications  generally  re- 
quire that  all  extra  work  shall  be  done  only  upon  a  written  order 
of  the  proper  authorities.  If  no  price  is  fixed  in  a  contract  for 
such  extras,  a  written  order  should  always  contain  the  amount  to 
be  allowed  for  the  extra  work  done,  so  that  when  a  bill  for  the  same 
is  presented  by  the  contractors  there  will  be  no  question  of  the 
amount  of  remuneration. 

Where  the  contractor  and  the  engineer  are  in  harmony,  extras 
are  very  often  ordered  in  by,  and  performed  under,  verbal  orders, 
even  when  this  clause  is  inserted  in  the  specifications.  The  im- 
portance, however,  of  observing  such  clause,  and  in  fact  all  clauses 
of  the  specifications,  by  the  contractor  as  well  as  the  city  officials, 
was  seen  in  carrying  out  a  sewer  contract  in  which  the  specifica- 
tions provided  that  no  sheeting  left  in  the  work  should  be  paid  for 
unless  it  was  so  ordered  by  a  written  order  from  the  Board  of 
Public  Works.  In  this  particular  case  sheeting  was  ordered  in 
verbally  by  the  Engineer  of  the  Board,  and  a  return  made  of  the 
same  by  the  inspector  in  charge.  When  the  final  estimate  was 
given  the  Board  of  Public  Works  refused  to  pay  for  the  sheeting, 
and,  in  a  suit  which  was  brought  to  settle  other  disputed  points  of 
the  same  contract,  the  court  decided  that  the  city  was  not  liable 
for  the  sheeting  because  it  had  not  been  left  in  in  accordance  with 
the  written  order  as  provided  by  the  specifications,  although  it  was 
ordered  in  verbally  and  deemed  necessary  by  the  Chief  Engineer  of 
the  Board. 
Alternative  Bids. 

It  is  sometimes  the  practice  in  receiving  bids  to  allow  con- 
tractors to  make  alternative  propositions,  that  is,  a  proposition  to 
do  the  work  for  a  certain  price  if  performed  with  a  certain  kind  of 
material  in  a  certain  manner,  or  for  another  price  if  performed  with 
other  material  in  a  certain  other  manner.  This  is  objectionable, 
as  it  makes  it  possible  to  have  two  lowest  bidders,  depending  on 
the  way  the  work  is  to  be  carried  out.  It  also  leaves  it  possible  for 
the  contract  to  be  awarded  to  one  bidder  at  one  price,  and  after  the 
'Contract  is  let  to  substitute  the  alternative  proposition  at  its  price, 
and  so  have  the  work  performed  eventually  by  a  contractor  who 


382        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

was  not  the  lowest  bidder.  Wherever  possible,  the  conditions  should 
be  so  studied  beforehand  as  to  be  able  to  decide  which  material 
is  better  for  any  particular  work,  and  call  for  bids  accordingly. 
Sometimes,  however,  the  question  of  deciding  is  an  economical 
one,  and  the  matter  of  cost  is  an  important  element  in  the  decision. 
In  that  event,  it  is  permissible  to  receive  alternative  bids,  but  as  a 
rule  the  practice  should  be  discouraged. 
General  Instructions. 

Attached  to  the  specifications  should  be  a  sheet  giving  general 
instructions  to  bidders,  telling  what  formal  requirements  are  called 
for  and  what  steps  it  is  necessary  to  take  in  order  that  their  bid 
should  be  received  and  be  in  proper  form.  In  order  to  facilitate 
the  canvass  of  bids  and  to  insure  uniformity  in  bidding,  blanks 
should  be  made  «out  for  each  bidder,  giving  estimated  quantities 
upon  which  bids  will  be  canvassed.  In  the  instructions  to  the 
bidder  should  be  inserted  a  clause  telling  at  what  hour  all  bids  are 
to  be  in.  This  time  should  not  be  varied  from,  and  as  a  rule  all 
bids  should  be  opened  at  the  time  specified  for  their  reception. 
It  often  occurs,  if  bids  are  allowed  to  remain  a  certain  time  after 
they  have  been  received,  that  one  or  possibly  more  may  come  in 
between  the  time  of  reception  and  opening.  If  these  should  all 
be  high  bids,  no  trouble  would  occur;  but  if  the  lowest  bid  should 
happen  to  be  one  that  was  received  after"  the  time  advertised  for 
the  bids  to  be  in,  complications  would  be  very  apt  to  arise.  Con- 
tractors who  have  complied  strictly  with  all  the  requirements  com- 
plain, and  rightly  too,  if  these  requirements  are  not  lived  up  to 
by  the  city,  and  it  seems  no  more  than  just  that  if  the  city  or 
corporation  calling  for  bids  require  the  contractor  to  live  up  to 
these  requirements,  it  should  do  so  itself. 
Certified  Check. 

On  every  work  of  any  magnitude  it  is  customary  to  have  a. 
certified  check  accompany  each  bid,  in  order  to  indemnify  the  city 
from  any  loss  or  damage  if  for  any  reason  the  successful  bidder 
should  not  be  able  to  enter  into  the  contract.  It  is  also  sometimes 
required,  in  addition  to  this  certified  check,  that  the  bidder  give  the 
names  of  the  persons  or  surety  company  who  will  sign  all  bonds 
for  the  performance  of  the  work  in  case  the  contract  should  be 
awarded  to  the  bidder.  It  does  not  seem  necessary,  and  in  some 
cases  it  works  hardship,  to  require  both  certified  check  and  the 


PLANS  AND  SPECIFICATIONS.  383 

names  of  the  bondsmen.  A  certified  check  should  certainly  be 
sufficient  to  indemnify  the  city  for  any  damage,  and  in  case  satis- 
factory bondsmen  could  not  be  provided  the  city  would  have  re- 
course to  the  check. 

The  amount  of  this  check  should  be  as  small  as  possible  and  yet. 
give  the  city  adequate  security.  It  is  generally  customary  to  re- 
quire a  percentage  of  the  amount  of  the  bid.  This,  perhaps,  for 
a  general  rule,  is  as  good  as  any;  although  in  some  contracts  where 
it  is  necessary  for  the  work  to  be  done  as  soon  as  possible,  the 
time  lost  in  readvertising  would  be  of  considerable  value,  while  in 
others  the  delay  would  be  no  material  damage,  so  that  it  would 
probably  be  more  satisfactory  to  establish  an  arbitrary  sum  for  each 
contract.  Five  per  cent  of  the  amount  of  the  bid  is  the  ordinary  re- 
quirement. 

Error  in  Bid. 

It  is  often  found  or  claimed,  while  the  bid  is  being  read,  that 
an  error  has  been  made  in  making  out  same,  and  an  application 
made  for  an  opportunity  to  make  a  correction.  To  allow  this 
would  be  to  establish  a  dangerous  precedent.  The  contractor  must 
take  certain  chances.  He  takes  work  by  contract  so  that  he  may 
make  more  than  ordinary  day's  wages,  and  if  an  error  should  occur 
so  that  he  is  compelled  to  do  a  certain  amount  of  work  for  less 
than  the  market  price,  or  bids  so  high  on  some  item  by  mistake 
that  he  loses  his  contract,  he  must  abide  by  the  letter  of  the  bid,, 
trusting  for  his  loss  in  one  case  to  be  made  up  by  gain  in  another. 
A  variation  from  this  rule  will  open  the  way  for  endless  trouble,, 
and  for  claims  of  errors  where  none  exist. 

Withdrawal  of  Bid. 

No  changes  or  withdrawals  should  be  permitted  after  any  bids, 
are  opened.  If,  however,  the  contractor  should  tender  his  bid 
some  hours  in  advance  of  the  final  closing,  and  wish  to  make 
changes  in  the  same,  there  should  be  no  objection  to  his  having  it 
returned  prior  to  the  expiration  of  the  time  for  the  receiving  of 
the  bids. 

Indorsement  of  Bids. 

In  order  that  there  may  be  no  question  as  to  whose  bid  any 
package  may  contain,  all  envelopes  should  be  indorsed  with  the 
name  of  the  bidder  and  the  work  which  he  proposes  to  carry  out. 


384        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Bond. 

Before  any  contract  is  executed  by  the  city,  a  bond  should  be 
signed  by  responsible  parties  guaranteeing  that  the  contractor  will 
carry  out  the  provisions  of  the  contract.  The  amount  of  this  bond 
must  be  determined  by  the  nature  of  the  work.  It  should  be  a 
fixed  amount,  decided  much  upon  the  same  principle  as  that  gov- 
erning the  amount  of  the  certified  check,  that  is,  the  damage  that 
the  city  is  liable  to  be  put  to  from  the  failure  or  delay  in  the  carry- 
ing out  of  the  work.  It  should  be  large  enough  to  provide  for 
any  loss  of  time  on  account  of  the  necessity  of  cancelling  the  con- 
tract and  readvertising  the  work,  and  also  to  make  good  any  dif- 
ference in  the  cost  from  the  original  contract  price  and  what  was 
actually  required  to  perform  the  work.  The  former  must  be  deter- 
mined by  the  location  and  character  of  the  work,  and  the  latter  by 
the  prices  for  the  different  items  in  the  contract. 
Time  for  Completion. 

All  contracts  contain  the  provision  that  the  work  shall  be  done 
by  a  specified  time  or  in  a  specified  number  of  working  days,  and 
generally  provide  for  a  penalty  to  be  paid  by  the  contractor  for 
each  day  in  excess  of  the  stated  time.  It  is  necessary  to  insert 
such  a  provision  in  all  contracts.  Otherwise  it  would  be  possible 
for  a  contractor  to  begin  a  piece  of  work  and,  after  it  was  partially 
completed,  to  leave  it  for  some  other  and  more  profitable  contract, 
or  to  dilly-dally  on  the  street  to  the  inconvenience  and  detriment 
of  the  public  at  large.  The  engineer,  however,  in  determining  the 
time  should  be  sufficiently  liberal  to  enable  the  contractor  to  finish 
within  the  specified  time  if  he  uses  reasonable  diligence. 
Penalty. 

The  question  of  penalty,  however,  is  one  that  should  be  taken 
up  with  a  great  deal  of  care.  It  must  be  considered  that  it  requires 
two  parties  to  make  a  contract,  and  if  a  penalty  is  required  for  any 
excess  of  time  employed,  and  no  bonus  given  if  the  work  is  per- 
formed sooner  than  the  specified  time,  it  is  questionable  whether 
such  penalty  could  be  enforced.  It  would  seem,  too,  if  the  work 
was  of  such  a  nature  that  the  time  of  completion  was  important, 
that  it  would  be  just  to  both  parties  to  require  a  penalty  if  the 
time  limit  were  exceeded,  and  to  pay  a  bonus  if  the  work  were  com- 
pleted inside  of  the  specified  time.  This  is  the  general  practice  on 
large  and  very  important  contracts.  If,  however,  the  contractor 


PLANS  AND  SPECIFICATIONS.  385 

has  bid  a  certain  price  for  agreeing  to  finish  within  a  certain  time, 
which  possibly  is  higher  than  that  of  the  bidder  who  proposes  to 
do  it  in  a  longer  time,  the  question  is  different,  for  in  the  latter 
case  the  contractor  receives  extra  compensation  for  early  com- 
pletion, and  if  he  exceeds  the  limit,  a  penalty  should  and  un- 
doubtedly could  be  enforced. 
Maintenance. 

In  specifications  for  street  improvements  of  any  kind  it  is  gen- 
erally provided  that  the  work  shall  be  maintained  and  kept  in 
repair  for  a  certain  length  of  time.  When  asphalt  pavements 
were  first  introduced  in  this  country  it  was  necessary  for  the  con- 
tractor to  agree  to  keep  the  pavement  in  repair  for  five  years  in 
order  to  have  any  city  adopt  them.  The  material  was  new  and  no 
-city  would  run  the  risk  of  paying  the  price  asked  for  an  unknown 
and  uncertain  pavement;  so  that  when  the  contracts  were  made 
they  contained  a  clause  binding  the  contractor  to  keep  them  in 
good  repair  for  five  years,  whereby  the  city  in  each  case  was  cer- 
tain of  a  good  pavement  for  a  definite  period.  The  conditions, 
however,  at  the  present  time  are  very  different.  Asphalt  pave- 
ments are  well  established  and  have  come  to  stay,  and  the  ques- 
tion of  guarantee,  as  to  its  length  and  exact  meaning,  is  very 
important. 
Payments. 

The  method  of  paying  for  the  original  pavement  and  of  keep- 
ing it  in  repair  varies  in  different  cities.  In  some  places  the 
original  cost  is  paid  by  special  assessment,  and  the  repairs  by  a  gen- 
eral tax.  In  such  cases  as  this  the  guarantee  period  must  be 
•carefully  determined  upon.  It  has  been  adjudicated  in  the  courts 
many  times,  and  the  established  limit  has  been  that  a  guarantee 
period  of  five  years  can  be  enforced  in  a  contract  for  an  asphalt 
pavement  the  payment  for  which  is  derived  by  general  assessment, 
but  that  it  cannot  when  the  cost  of  repairs  or  repaving  is  defrayed 
by  general  tax.  In  New  York  City  all  contracts  for  asphalt  pave- 
ment requiring  payment  by  special  assessment  are  made  with  a 
guarantee  period  of  five  years,  while  in  those  where  the  expense  is 
borne  by  a  general  tax  the  guarantee  is  made  ten  and  sometimes 
fifteen,  years. 
Guarantee. 

While  the  original  asphalt  pavements  were  laid  with  the  inten- 


386        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

tion  of  being  kept  and  maintained,  without  any  expense  to  the 
city,  for  a  period  of  five  years,  it  is  questionable,  unless  specifically 
defined,  just  what  is  meant  by  the  terms  "  guarantee  "  and  "  main- 
tenance." Cities  as  a  rule  consider  that  it  means  that  they  shall 
be  at  no  expense  whatever  for  the  care  of  these  pavements  during 
the  guarantee  period.  The  contractors,  however,  maintain  that 
their  guarantee  covers  simply  that  the  work  shall  be  done  in  a 
proper  manner  and  with  good  materials;  that  if  any  unforeseen 
circumstances  arise,  causing  damage  to  the  pavement,  they  are 
not  compelled  to  repair  it  without  special  compensation.  Fires, 
settlements  of  sewers,  causing  breaks  in  the  pavement,  are  all 
cases  in  point.  Specifications,  therefore,  should  clearly  define  just 
what  is  intended,  and  it  would  seem  that  when  a  guarantee  is  given 
that  the  work  will  be  done  properly  and  good  materials  furnished, 
nothing  more  could  be  required  or  expected  of  the  contractor,  on 
the  principle  laid  down  before,  that  the  contractor  should  know- 
all  of  the  conditions  under  which  he  bids,  and  that  the  city  should, 
pay  the  cost  of  any  unforeseen  damage  to  the  pavement. 

As  to  how  long  the  guarantee  shall  run  is  also  a  mooted  ques- 
tion. For  some  reason  five  years  has  seemed  to  be  taken  as  the- 
unit  for  asphalt  pavement,  although  in  many  cases  contracts  have- 
been  made  with  ten  and  fifteen  years7  guarantee.  Sometimes  the- 
cost  of  guarantee  has  been  included  in  the  original  price  per  square 
yard.  In  other  cases  the  contract  has  provided  for  the  original 
price  per  square  yard,  the  pavement  to  be  maintained  without  ex- 
pense for  five  years,  and  then  for  an  additional  five  years  for  a 
specified  price  per  year. 

In  1898  a  contract  for  laying  asphalt  pavement  was  made  in 
Minneapolis,  Minn.,  for  a  certain  price  per  square  yard,  with  a  ten 
years'  guarantee,  and  the  additional  price  of  10  cents  per  yard  per 
year  for  a  second  period  of  ten  years. 

Newark,  N.  J.,  has  asked  for  bids  for  a  five-year  guarantee,  and 
has  specified  an  additional  price  of  5  cents  per  yard  per  year  for  an 
additional  ten  years. 

Other  cities  have  called  for  stipulated  prices  per  yard  for  a 
certain  guarantee  period,  with  the  option  of  making  an  additional 
contract  for  a  specified  price  per  yard  per  year. 

Previous  to  consolidation  New  York  City  required  asphalt  pave- 
ments paid  for  by  the  general  public  to  be  maintained  for  fifteen 


PLANS  AND  SPECIFICATIONS.  387 

years.  The  specifications  provided  that  on  the  completion  of  the 
work  TO  per  cent  of  the  contract  price  should  be  paid  to  the  con- 
tractor. Of  the  remaining  30  per  cent,  one-tenth  was  to  be  paid 
each  year,  beginning  five  years  from  the  date  of  final  acceptance. 
The  present  contracts  call  for  a  guarantee  of  ten  years  with  a  re- 
serve of  20  per  cent,  one-fifth  of  which  shall  be  paid  each  year, 
beginning,  as  above,  five  years  from  date  of  completion  of  the 
work. 

The  old  city  of  Brooklyn  required  a  five-year  guarantee  on  all 
asphalt  pavement,  but  made  payment  in  full  upon  the  completion 
of  the  work,  relying  upon  the  bond  wholly  for  the  carrying  out  of 
the  maintenance  portion  of  the  contract.  Omaha,  Neb.,  also  re- 
quired five  years'  maintenance,  but  reserved  15  per  cent  of  the 
contract  price  until  the  end  of  the  guarantee  period.  The  contrac- 
tor was,  however,  allowed  to  purchase  city  bonds  and  deposit  them 
with  the  city  treasurer,  in  lieu  of  this  reserve,  and  thus  draw  in- 
terest upon  the  amount  withheld. 

Upon  granite,  brick,  or  other  pavement,  where  it  can  soon  be 
determined  whether  there  are  any  faults  in  either  material  or  con- 
struction, no  long-time  guarantee  is  necessary.  At  the  end  of  nine 
months  any  defects  from  the  above  causes  will  have  been  developed 
and  can  be  repaired,  and  there  would  be  no  good  reason  for  requir- 
ing any  reserve  fund  to  be  longer  held. 

When  the  work  is  completed  the  entire  amount  should  be  paid 
less  ten  or  fifteen  cents  per  yard  of  pavement,  according  to  the 
character  of  the  work.  When  the  guarantee  period  has  expired  and 
any  necessary  repairs  have  been  made,  the  above  amount  should  be 
paid  the  contractor. 

The  specifications  for  stone  pavements  of  Cleveland,  0.,  require 
a  guarantee  that  the  pavement  be  kept  in  good  condition  for  five 
years,  and  provide  that  any  paving-stones  at  the  end,  or  during 
the  term  of  said  guarantee,  which,  in  the  opinion  of  the  Director 
of  Public  Works  or  Chief  Engineer,  show  a  greater  loss  than  10 
per  cent  of  their  original  or  specified  depth,  shall  be  taken  up  by 
or  at  the  expense  of  the  contractor,  and  good  and  acceptable  ma- 
terial substituted  therefor,  and  the  pavement  placed  in  good  and 
satisfactory  condition. 

To  provide  for  the  enforcement  of  the  above  2£  cents  per  square 
foot  is  retained  for  each  and  every  square  foot  of  pavement,  flag- 


388        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

ging,  and  cross-walk.  The  amount  retained  from  the  final  estimate 
is  deposited  in  the  city's  name  in  some  bank  designated  by  the  city, 
and  all  interest  and  dividends  accruing  become  the  property  of  the 
contractor  if  the  provisions  of  the  contract  have  been  satisfactorily 
carried  out. 
Details  of  Work. 

To  just  what  extent  it  is  proper  for  any  city  or  corporation  to 
specify  the  details  with  which  work  shall  be  carried  on  when  it 
is  to  be  maintained  for  a  specified  time  is  often  questioned.  The 
contractor  claims  that  he  is  under  contract  to  maintain  pavement 
for  a  certain  length  of  time,  and  it  is  for  his  best  interest  to  do  the 
work  in  a  proper  manner,  and  that  he  should  be  allowed  to  do  it 
according  to  his  judgment.  The  engineer,  on  the  other  hand,, 
argues  that  the  contractor  knew  the  specifications  and  requirements 
before  he  bid,  and  if  he  could  not  get  good  results  from  those  speci- 
fications, he  should  either  have  protested  before  putting  in  his 
bid  or  making  his  contract,  or  else  refused  to  have  anything  to  do 
with  the  work. 

The  contention  of  the  contractor  is  hardly  valid,  for  even  if  he 
enter  into  a  contract  to  maintain  the  pavement  for  a  term  of  five 
years  or  fifteen  years,  he  is  also  under  contract  to  leave  it  in  good 
condition  at  the  end  of  that  time,  and  it  is  for  the  city's  interest 
to  have  it  left  in  such  condition  at  the  end  of  the  guarantee  period 
that  it  will  last  for  as  long  a  time  as  possible  afterwards,  with  little 
repair.  So  that  there  seems  to  be  no  question  but  that  the  city  has, 
the  right  to  enforce  all  the  requirements  of  the  specifications.  This 
assumes,  however,  that  the  city  will,  as  in  fact  it  must,  employ  a 
competent  engineer  to  make  the  specifications  so  that  no  impossible 
requirements  are  inserted. 
Unbalanced  Bids. 

Another  source  of  great  trouble  to  the  engineer  in  the  carrying 
out  of  contracts  is  unbalanced  bids.  When  different  items  are 
given  for  the  amount  of  work  to  be  performed  and  there  is  any 
uncertainty  as  to  these  quantities,  the  shrewd  contractor  often  goes 
over  the  work  in  advance  of  the  bidding,  in  order  to  verify  these 
quantities  and  make  his  own  estimate  as  to  the  probability  of  their 
being  correct.  If  he  thinks  they  are  liable  to  be  varied  in  the 
carrying  out  of  the  work,  he  will  make  a  high  price  for  one  item 
and  a  low  price  for  another,  so  that  he  will  be  the  lowest  bidder  on 


PLANS  AND  SPECIFICATIONS.  389 

the  quantities  as  given,  but  be  higher  on  the  work  as  completed. 
While  this  would  do  no  harm  on  contracts  where  the  quantities  are 
not  changed,  it  often  does  cause  great  trouble  if  for  any  reason  it 
is  desired  to  make  any  changes.  It  also  permits  the  engineer,  if  in 
collusion  with  the  contractor,  to  change  some  items,  reducing  those 
of  small  price  and  increasing  those  of  the  higher  price,  to  the  great 
benefit  of  the  contractor. 

It  is  not  always  easy  to  determine  what  is  an  unbalanced  bid. 
Often  the  conditions  may  be  such  that  one  contractor  may  be  able 
to  do  a  piece  of  work,  or  one  portion  of  it,  for  a  price  which  would 
seem  to  make  it  an  unbalanced  bid,  when  it  was  strictly  legitimate. 
In  some  way  he  might  have  an  advantage  over  another  contractor. 
But  there  are  cases  where  it  is  plain  to  be  seen  on  the  face  of  it 
that  the  bid  is  unbalanced.  In  every  case  of  this  kind  the  bid 
should  be  thrown  out  without  hesitation,  provision  having  been 
made  in  the  specifications  for  such  action.  One  of  the  best,  if  not 
the  best,  of  the  methods  of  overcoming  unbalanced  bids  is  that 
adopted  by  Jersey  City,  N.  J.  It  it  customary  there  for  the  En- 
gineer, after  carefully  studying  the  market,  to  establish  a  price 
for  each  item  that  is  called  for  in  the  work,  and  require  all  bidders 
to  bid  a  certain  percentage  above  or  below  this  standard,  and  apply 
this  percentage  to  every  item  of  the  schedule.  This  absolutely 
prevents  any  trouble  from  unbalanced  bids,  and  certainly  seems 
fair  to  both  city  and  contractor. 
Combinations  among  Contractors. 

Another  plan  of  protecting  the  city,  not  from  unbalanced  bids, 
but  from  contractors  making  combinations  among  themselves,  has 
been  adopted  in  Toronto,  Can.  There  the  City  Engineer  himself 
puts  in  a  bid  to  the  city,  agreeing  to  do  the  work  for  what  he  con- 
siders a  fair  and  reasonable  price.  If  he  should  be  the  lowest  bid- 
der, the  work  Is  awarded  to  him  and  carried  out  by  the  city  by  day's 
labor  under  the  Engineer's  supervision.  The  contractors,  knowing 
this  is  to  be  done,  realize  that  there  is  no  opportunity  for  obtaining 
an  extravagant  price,  and  in  consequence  generally  bid  with  the 
expectation  of  a  reasonable  profit. 
Plans. 

The  plans  for  the  paving  of  a  street  should  show  first  the  limits 
of  the  contract  on  the  main  and  on  all  of  the  cross  streets.  It 
should  show  the  location  of  all  the  cross-walks  to  be  laid,  and  all 


390        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

special  work  called  for.  It  should  show  the  cross-sections  of  the 
finished  pavements,,  and  give  every  detail  of  construction.  The 
profile  should  show  the  amount  of  excavation  and  embankment 
for  the  entire  length  of  the  street.  It  should  show  the  existing 
surfaces  of  both  property  lines  and.  also  the  centre,  so  that  the 
contractor  would  know  in  exactly  what  parts  the  excavation  and 
embankment  were  located,,  and  thus  be  able  to  determine  the  dis- 
tance that  the  earth  would  be  hauled.  The  plans  should  also 
show  the  quantities  of  each  kind  of  work  required.  After  the 
contract  has  been  awarded,  the  contractor  should  sign  the  plans, 
which  should  become  a  part  of  the  contract,  as  should  also  the 
specifications. 

The  foregoing  remarks  on  the  Plans  and  Specifications  are 
general,  although  mainly  referring  to  pavement-construction. 

The  specifications  which  follow  are  suggested  for  general  use 
for  the  original  improvement  of  streets  that  have  never  been 
graded.  These  specifications  are  made  up  mainly  of  the  plans  and 
specifications  for  New  York  City,  modified  according  to  the  ideas 
of  the  author  and  the  result  of  twenty  years'  experience  in  munici- 
pal work.  They  embody  what  is  considered  the  best  practice  of 
the  principal  cities  of  the  country.  The  section  relating  to 
Medina-sandstone  pavements  has  been  taken  almost  entirely  from 
the  specifications  of  Cleveland,  0.,  and  that  for  asphalt  blocks  from 
those  of  the  Hastings  Pavement  Co. 

While  these  specifications  are  general,  they  are  supposed  to  be 
so  made  up  that  they  can  be  applied  and  used  in  any  city  in  the 
country  by  making  the  changes  required  by  local  conditions  and 
laws.  Some  modifications  would  be  required  for  repaving  work, 
but  for  the  actual  work  of  pavement-construction  they  are  recom- 
mended for  general  use. 

Notice  to  Bidders. 

Bidders  must  satisfy  themselves,  by  personal  examination  of 
the  location  of  the  proposed  work  and  by  such  other  means  as 
they  may  prefer,  as  to  the  accuracy  of  the  estimated  quantities, 
and  shall  not,  at  any  time  after  the  submission  of  a  bid,  dispute 
or  complain  of  such  statement  or  estimate  of  the  Engineer,  nor 
assert  that  there  was  any  misunderstanding  in  regard  to  the  nature 
or  amount  of  the  work.  The  quantities  given  herewith  are  sup- 


PLANS  AND  SPECIFICATIONS.  391 

posed  to  be  accurate,  and  are  estimated  by  the  City  Engineer  for 
the  purpose  of  determining  the  lowest  bidder,  but  final  payment 
will  be  made  on  measurements  made  of  work  actually  performed. 
Each  bidder  must  deposit  with  the  Commissioner  of  Highways, 
at  least  four  days  before  making  his  bid,  samples  of  the  materials 
he  intends  to  use,  according  to  the  character  of  the  work  called  for, 
as  follows: 

1.  A  specimen  of  refined  asphalt,  with  a  certificate  stating 
where  the  material  was  mined. 

2.  A  specimen  of  the  asphaltic  cement,  with  a  statement  of 
the  formula  to  be  used  in  the  composition  of  the  mixture  for  the 
wearing  surface. 

3.  A  sample  of  not  less  than  four  pounds  of  the  paving  mix- 
ture as  it  will  be  laid  upon  the  street. 

4.  Not  less  than  twelve  bricks  which  are  proposed  to  be  used. 

5.  A  sample  block  of  either  stone  or  asphalt. 

6.  Additional  specimens  of  all  kinds  must  be  furnished  as  often 
as  may  be  required  during  the  progress  of  the  work. 

No  bid  will  be  received  or  considered  unless  the  deposits  of 
material  referred  to  above  are  made  with  the  City  Engineer  within 
the  time  prescribed. 

Any  bid  accompanied  by  samples  which  do  not  come  up  to  the 
standard  required  by  these  specifications  will  be  regarded  as  in- 
formal. 

No  proposals  will  be  received  or  considered  unless  accompanied 
by  either  a  certified  check  drawn  to  the  order  of  the  Comptroller, 
or  of  money  equal  to  five  per  cent  of  the  amount  of  the  security 
required  for  the  faithful  performance  of  the  work.  Such  check 
or  money  must  not  be  inclosed  in  the  sealed  envelope  contain- 
ing the  proposal,  but  must  be  handed  to  the  officer  or  clerk 
who  has  charge  of  the  proposal-box,  and  no  proposal  can  be  de- 
posited in  said  box  until  such  check  or  money  has  been  examined 
and  found  to  be  correct.  All  such  deposits,  except  those  of  suc^ 
cessful  bidders,  will  be  returned  to  the  persons  making  the  same 
after  the  contract  is  awarded.  If  the  successful  bidder  shall  re- 
fuse or  neglect,  within  five  days  after  notice  that  the  contract  has 
been  awarded  to  him,  to  execute  the  same,  the  amount  of  the 
deposit  made  by  him  shall  be  forfeited  to  and  retained  by  the  city 
..  .  .  as  liquidated  damages  for  such  neglect  or  refusal;  but  if  he 


392        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

shall  execute  his  contract  within  the  time  aforesaid,  the  amount 
of  his  deposit  shall  be  returned  to  him. 

SPECIFICATIONS  FOR  GRADING  AND  PAVING  WITH 
PAVEMENT   ON  A   CONCRETE  FOUNDATION. 

(1)  The  work  to  he  done  shall  consist  of  grading  the  entire 
width  of  the  street,  setting  curbstones  and  heading-stones  if  re- 
quired, laying  and  relaying  the  cross-walks  where  so  required,  and 
laying  -         -  pavement  on  a  -         -  foundation  on  the  roadway 
of-         -  Street  from Street  to  -        -Street. 

(2)  All  the  materials  furnished,  and  all  the  work  done,  which,, 
in  the  opinion  of  the  City  Engineer,  shall  not  be  in  accordance- 
with  the  specifications  shall  be  immediately  removed,  and  other 
materials  furnished,  and  work  done,  that  shall  be  in  accordance 
therewith. 

Before  any  materials  are  placed  upon  the  street  the  City  En- 
gineer shall  approve  of  the  quality  and  finish  of  samples  of  the: 
same  which  shall  be  furnished  at  his  office.  These  shall  include- 
the  samples  referred  to  on  page  ,  and  also  a  sample  of  the 

paving-blocks  to  be  used  in  the  work. 

(3)  The  work  under  this  specification  is  to  be  prosecuted  at 
and  from  as  many  different  points  in  such  part  or  parts  of  the 
streets  on  the  line  of  the  work  as  the  City  Engineer  may,  from 
time  to  time,  determine,  and  at  each  of  said  points  inspectors  may 
be  placed  on  the  day  designated  for  the  commencement  of  the 
work. 

(4)  The  right  to  construct  any  sewer  or  sewers,  receiving-basins 
or  culverts,  or  to  build  up  or  adjust  any  manholes,  or  to  reset  or 
renew  any  frames  and  heads  for  sewer  or  subway  manholes,  or  for 
water  or  gas  stop-cocks,  or  to  lay  gas-  or  water-pipes,  or  to  con- 
struct necessary  appurtenances  in  connection   therewith  in  said 
street  or  avenue,  or  to  grant  permits  for  house-connections  with 
sewers,  or  with  water-  or  gas-pipes,  or  for  any  other  underground 
or  subway  construction,  or  to  alter  and  relay  railroad-track,  at  any 
time  prior  to  the  laying  of  the  new  pavement  over  the  line  of  the 
same,  is  expressly  reserved  by  said  City  Engineer;    and  said  City 
Engineer  reserves  the  right  of  suspending  the  work  on  said  pave- 
ment, on  any  part  of  the  line  of  said  street  or  avenue  at  any  timer 


PLANS  AND  SPECIFICATIONS.  393 

during  the  construction  of  the  same,  for  the  purposes  above  stated, 
without  any  compensation  to  the  Contractor  for  such  suspension 
other  than  extending  the  time  for  completing  the  work  as  much  as 
it  may,  in  the  opinion  of  the  said  City  Engineer,  ha*T-K  been  de- 
layed by  such  suspension;  and  the  said  Contractor  shall  ***t  inter- 
fere with  or  place  any  impediment  in  the  way  of  any  person  or 
persons  who  may  be  engaged  in  the  construction  of  such  sewer  or 
sewers,  or  in  making  connections  therewith,  or  doing  other  work 
above  specified,  or  in  the  construction  of  any  receiving-basins  or 
culverts. 

(5)  In  case  there  shall  be  at  the  time  stipulated  for  the  com- 
mencement of  the  work  any  earth,  rubbish,  or  other  incumbrance 
(building  material  for  which  a  proper  permit  has  been  issued  is  not 
herein  included)  on  the  line  of  the  work,  and  Hot  required  by  the 
Department,  the  same  is  to  be  removed  at  the  expense  of  the  Con- 
tractor. 

(6)  Grading. — The  entire  width  of  the  street  is  to  be  regulated 
and  graded,  in  accordance  with  the  grade  as  shown  upon  the  profile 
or  map  on  file  in  the  office  of  the  City  Engineer.    The  carriageway 
and  sidewalks  to  be  shaped  as  per  cross-section  shown  on  the  plans. 
That  portion  of  the  street  which  is  above  the  grade-lines  to  be 
excavated,  and  such  parts  as  are  now  below  the  grade-lines  to  be 
filled  in,  in  the  manner  hereinafter  provided,  and  the  surplus  earth 
not  used  for  filling  to  be  removed  from  the  street.     If,  owing  to 
the  unfitness  of  the  present  material  for  a  foundation,  it  is  con- 
sidered necessary  by  the  Engineer  to  remove  it  to  a  greater  depth 
and  substitute  other  material,  such  removal  and  refilling  will  be 
paid  for  by  the  cubic  yard  at  the  prices  bid  for  excavation  and  em- 
bankment, except  as  hereinafter  specified. 

The  slopes  in  excavation  shall  be  one  and  a  quarter  horizontal 
to  one  vertical. 

The  embankment  shall  be  formed  of  good,  wholesome  earth, 
sand,  gravel,  or  clean  ashes.  No  house-ashes  containing  garbage 
or  rubbish,  no  vegetable  matter  or  debris  of  any  kind  will  be  al- 
lowed. The  slopes  of  the  embankment  shall  be  one  and  a  half  hori- 
zontal to  one  vertical. 

No  allowance  will  be  made  the  Contractor  in  any  case  for  settle- 
ment, shrinkage,  or  additional  slopes.  If  any  material  shall  be 
encountered  in  excavating  which  is  considered  especially  adapted 


394        8TEEET  PAVEMENTS  AND  PAVING  MATERIALS. 

for  the  foundation,  it  shall  be  placed  aside  when  so  directed,  and 
used  at  the  proper  time  for  that  purpose. 

The  embankment  is  to  be  made  from  material-  excavated  on  the 
street  where  there  is  a  sufficient  quantity  of  such  material.  Where 
the  amount  of  excavation  is  less  than  the  amount  of  embankment 
the  Contractor  must  supply  the  deficient  material.  The  price  bid 
for  grading  shall  be  applied  to  whichever  amount  shall  be  in  ex- 
cess. 

(7)  Grading  Sidewalks. — All  stone  shall  be  dug  out  of  the  side- 
walks,  to  three  inches  below  the  finished  grade  thereof,  and  the 
holes  filled  to  the  grade  of  the  sidewalks  with  clean  sand  or  gravel. 
The  sidewalks  to  have  a  slope  of  six  inches  from  the  line  of  the 
street  to  the  curb. 

(8)  Preparation  of  Roadbed. — The  carriageway  shall  be  thor- 
oughly rolled  with  a  ten-ton  steam-roller,  all  soft  spots  having  been 
excavated  and  filled  with  gravel  or  other  suitable  material  until  the 
whole  roadway  has  been  thoroughly  consolidated  and  finished  to 
the  following  depths  below  the  surface  of  the  completed  pavement: 

For  asphalt  nine  inches;   for  asphalt  block  seven  and  one-half 
inches:  for  granite  on  sand  twelve  inches;   for  granite  on  concrete 
fifteen  inches;  for  Medina  sandstone  on  concrete  thirteen  and  one 
half  inches;   and  for  vitrified  brick  eleven  inches. 

(9)  Cross-walks. — The  cross-walks  shall  consist  of  three  courses 
of  stone.     The  stone  to  be  of  the  same  quality  as  the  blocks,  the 
side  and  ends  to  be  squared  and  free  from  all  winds,  seams,  and 
other  imperfections;   each  stone  to  be  not  less  than  four  feet  nor 
more  than  six  feet  in  length,  one  and  one-half  feet  wide,  and  not 
less  than  six  nor  more  than  eight  inches  thick  throughout,  to  be 
dressed  to  an  even  face  on  top,  sides,  and  end.     The  ends  of  the 
stones  are  to  be  cut  to  such  curves,  when  necessary,  as  may  be 
directed,  and  all  to  form  close  and  even  joints  from  top  to  bottom 
when  laid.     Where  cross-walks  are  at  right  angles  to  the  line  of 
travel  all  joints  shall  be  cut  with  a  bevel  of  six  inches. 

The  Contractor  shall  lay  one  row  of  stone  blocks  between  the 
courses  of  bridge-stones. 

The  cross-walk  stones  must  be  firmly  bedded  on  the  same  foun- 
dation as  the  pavement,  and  set  true  to  line  and  grade.  The  courses 
must  be  so  laid  that  the  transverse  joints  will  be  broken  by  a  lap 
of  at  least  one  foot. 


PLANS  AND  SPECIFICATIONS.  395 

Any  old  cross-walks  now  on  the  line  of  the  street  or  adjacent 
fo  the  new  pavement  shall  be  relaid  by  the  Contractor,  when  so 
directed,  in  the  manner  above  described,  without  any  charge  there- 
for. 

(10)  Curbstones. — The  new  curb  shall  be  of  the  best  quality 
of ,  hard,  sound,  and  free  from  seams  or  any  other  imperfec- 
tions.   It  shall  be  fifteen  inches  in  depth,  not  less  than  five  inches 
in  thickness,  and  the  back  shall  be  free  from  projections  of  more 
than  two  inches;   while  it  shall  have  a  uniform  thickness  of  five 
inches  for  at  least  three  inches  from  the  top. 

The  bottom  bed  shall  be  roughly  squared.  It  shall  be  in  length 
of  not  less  than  three  and  a  half  feet  nor  more  than  eight  feet. 

The  top  shall  be  axed  to  a  smooth  surface  with  a  bevel  of  one- 
half  inch  in  five  inches,  and  the  face  shall  be  out  of  wind  and  be 
brought  to  a  surface  which  shall  in  no  place  vary  more  than  a 
quarter  of  an  inch  from  a  true  plane. 

Special  care  must  be  taken  to  cut  the  joints  square  with  the 
face,  and  they  shall  be  close  for  the  full  thickness  for  not  less  than 
six  inches  from  the  top;  while  the  face  shall  have  close  joints  for 
its  entire  depth. 

All  curb,  unless  otherwise  directed,  shall  be  set  in  a  bed  of 
concrete  six  inches  in  depth  and  shall  have  a  backing  of  concrete 
six  inches  in  thickness,  extending  to  within  four  inches  of  the  top, 
as  shown  in  detail  plan.  The  concrete  bed  shall  be  laid  immediately 
before  the  curb  is  set,  and  the  backing  put  in  place  as  soon  as  set, 
and  as  much  of  the  concrete  foundation  for  the  pavement  as  may 
be  directed,  which  shall  not  be  less  than  one  foot;  the  object  being 
to  obtain  a  uniform  and  well-bonded  mass  of  concrete  behind, 
under,  and  in  front  of  the  curb.  When  set,  the  corners  of  the  top 
shall  be  in  a  straight  line  and  the  face  a  plane  surface. 

Should  the  concrete  in  front  of  the  curb  have  set  before  that  on 
the  remainder  of  the  street  shall  have  been  laid,  the  surface  shall  be 
carefully  cleaned  and  thoroughly  wet  before  any  fresh  concrete 
is  placed  against  it. 

Whenever  curb  is  set  for  stone  pavements  or  without  concrete, 
it  shall  be  eighteen  inches  deep,  but  in  all  other  respects  shall  con- 
form to.  the  above  conditions. 

(11)  Heading-stones. — When  asphalt  or  brick  pavement  joins 
the  pavement  of  another  kind  or  an  unpaved  street,  heading-stones, 


396        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

not  less  than  five  inches  thick  and  not  less  than  twelve  inches  in 
depth  and  in  lengths  of  not  less  than  two  feet,  shall  be  set  between 
the  new  and  the  old  pavement.  They  shall  be  set  upon  and 
firmly  bedded  in  a  bed  of  concrete  six  inches  in  depth.  These 
heading-stones  may  be  of  bluestone,  granite,  or  other  approved 
stone,  and  the  grade  of  the  adjacent  surface,  whether  paved  or  un- 
paved,  shall  be  adjusted  to  that  of  the  new  pavement  without 
extra  charge  therefor.  The  heading-stones  will  be  paid  for  as  pave- 
ment, and  must  be  included  in  the  price  bid  therefor. 

(12)  Concrete. — All  concrete  used  in  the  work  shall  be  made 
of  one  measure  of  natural  hydraulic  cement,  measured  in  the 
original  package,  two  measures  of  sand,  and  four  and  one-half 
measures  of  broken  stone,  If  the  mixing  is  done  by  hand,  the 
cement  and  sand  shall  be  thoroughly  mixed  dry  and  then  made 
Into  mortar  with  as  little  water  as  possible,  after  which  the  stone, 
•which  shall  have  been  previously  drenched  with  water,  shall  be 
added,  and  the  mass  thoroughly  mixed  until  all  of  the  stones  shall 
have  become  coated  with  mortar,  when  it  shall  be  promptly  placed 
into  position  and  rammed  until  the  water  flushes  to  the  surface. 
The  mixing  shall  be  done  upon  suitable  wooden  platforms  as  may 
Le  directed  by  the  Engineer. 

If  a  concrete-mixing  machine  be  used,  the  cement  and  sand 
shall  be  mixed  as  above,  and  precaution  must  be  taken  to  insure 
the  proper  proportion  of  each  of  the  materials,  so  that  the  re- 
sultant mixture  shall  be  uniform  in  quality.  The  cement,  sand, 
and  stone  must  be  placed  upon  board  platforms  and  kept  free 
from  dirt. 

Great  care  must  be  exercised  to  make  the  surface  of  the  con- 
crete exactly  parallel  to  and  -  -  inches  below  the  finished  pave- 
ment. The  concrete  shall  be  protected  from  the  weather  until 
set.  Should  the  concrete  at  any  time  oe  considered  by  the  En- 
gineer to  be  poorly  mixed  or  not  to  be  setting  properly,  such  por- 
tion shall  be  taken  up  and  replaced  with  satisfactory  material. 

The  cement  used  shall  be  equal  to  the  best  quality  of  freshly 
ground  American  cement.  It  shall  be  delivered  on  the  street  at 
least  forty-eight  hours  before  the  mixing  of  concrete  is  commenced, 
and  no  cement  shall  be  used  until  it  shall  have  been  tested,  and  ac- 
cepted by  the  Engineer. 

No  exact  requirement  will  be  made  for  the  tensile  strength  of 


PLANS  AND  SPECIFICATIONS.  397 

the  cement.  But  when  the  samples  are  submitted,  the  City  En- 
gineer will  test  them  according  to  such  a  standard  as  may  be 
adopted  for  each  particular  brand;  the  object  being  to  ascertain 
and  maintain  the  normal  strength  of  each  kind  of  cement  offered 
and  accepted. 

The  sand  shall  be  good,  clean,  coarse,  sharp  sand,  free  from 
loam  or  dirt. 

The  stone  shall  be  equal  in  quality  to  good  limestone,  entirely 
free  from  dust  and  dirt,  and  of  such  size  that  it  will  pass  through 
a  screen  having  holes  three  inches  in  diameter,  and  be  retained 
by  a  screen  having  holes  one  inch  in  diameter  and  as  evenly  graded 
between  the  two  extremes  as  possible. 

No  concrete  can  be  used  which  shall  have  been  mixed  more  than 
thirty  minutes.  No  carting  or  wheeling  will  be  allowed  on  the  con- 
crete until  it  is  sufficiently  set.  When  connection  is  to  be  made 
with  any  section  which  shall  have  set  or  partially  set,  the  edge  of 
such  section  must  be  thoroughly  cleaned  and  wet  so  as  to  insure  a 
.good  bond  with  the  new  work. 

Asphalt  Pavement. 

(13)  a.  The  pavement  proper  shall  consist  of  a  binder  course 
one  inch  in  thickness  and  a  wearing  surface  two  inches  thick. 

6.  Binder. — The  binder  course  shall  be  composed  of  suitable 
clean  broken  stone  passing  a  one-and-one-quarter-inch  screen,  not 
more  than  five  per  cent  of  which  shall  pass  a  No.  10  screen. 

The  stone  will  be  heated  in  suitable  appliances,  not  higher  than 
300°  F.  It  is  then  to  be  thoroughly  mixed  by  machinery  with 
•asphaltic  cement  made  as  per  sample  submitted  and  as  is  acceptable 
for  surface  cement,  at  300°  to  325°  F.,  in  proportion  of  about  6  to  7 
pints  of  cement  to  1  cubic  foot  of  stone. 

The  mixture  will  be  so  made  that  the  resulting  binder  has  life 
and  gloss  without  an  excess  of  cement.  Should  it  appear  dull  from 
overheating  or  lack  of  cement,  it  will  be  rejected. 

No  cement  composed  of  mixtures  of  asphalt  and  tar  will  be 
allowed.  While  hot  the  binder  will  be  hauled  upon  the  work, 
spread  upon  the  concrete,  to  such  a  thickness  that  when  compacted 
it  will  be  at  no  place  less  than  one  inch  in  thickness,  and  im- 
mediately rammed  and  rolled  until  it  shall  receive  its  required  com- 
pression. 


398        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Should  the  resulting  course  not  show  a  proper  bond.,  it  shall 
be  immediately  removed  and  replaced  by  the  Contractor,,  or,  should 
he  fail  to  do  so  in  twenty-four  hours  after  written  notice  from  the 
City  Engineer,  it  shall  be  removed  and  the  cost  charged  against 
any  moneys  which  are  or  may  become  due  him  from  the  city.  After 
compacting,,  the  upper  surface  of  the  binder  shall  be  exactly 
parallel  with  the  wearing  surface  of  the  pavement  to  be  laid. 

c.  Wearing  Surface. — Upon  this  foundation  must  be  laid  the 
wearing  surface,  or  pavement  proper,  the  basis  of  which  must  be 
asphaltic  cement  unmixed  with  any  of  the  products  of  coal-tar. 

The  standard  paving  mixture  for  the  wearing  surface  shall  be 
composed  of:  1.  Refined  asphalt;  2.  Heavy  petroleum  oil,  or  other 
approved  flux;  3.  Sharp,  clean  sand;  4.  Finely  powdered  mineral 
matter. 

d.  Asphalt. — The  refined  asphalt  for  use  in  the  manufacture 
of  the  asphaltic  cement  for  the  preparation  of  the  standard  paving 
mixture  shall  be  obtained  from  the  crude  natural  material,  and 
shall  be  in  all  respects  satisfactory  to  the  City  Engineer.     To 
accomplish  this,  the  crude  asphalt  must  be  specially  refined,  and 
brought  to   a  uniform  standard   of  purity,   quality,   and  specific 
gravity;    and,  after  having  been  so  refined,  it  shall  contain  not 
less  than  fifty-five  per  cent  of  bitumen  soluble  in  carbon  bisulphide, 
of  which  bitumen  at  least  sixty-eight  per  cent  shall  be  soluble  in 
Pennsylvania  petroleum  naphtha  of  a  specific  gravity  of  72  Beaume 
(boiling-points  80°   to  90°   centigrade);    it  shall  soften  at  from 
189°  to  192°  Fahrenheit,  and  flow  at  from  200°  to  210°  Fahrenheit; 
it  shall  volatilize  from  2J  to  3  per  cent  of  oil  in  ten  hours  at  a 
temperature  of  400°  Fahrenheit;    it  shall  have  a  specific  gravity 
of  not  more  than  1.38,  and  shall  be  free  from  all  manner  and  form 
of  adulteration,     After  the  evaporation  of  the  solvent,  the  pure 
bituminous  matter  soluble  in  carbon  bisulphide  shall  be  adhesive, 
malleable,  and  ductile  at  temperatures  ranging  from  70°  F'ahren- 
heit  to  its  liquefying-point.     It  shall  soften  at  168°  Fahrenheit 
and  flow  at  180°  Fahrenheit. 

The  above  properties  shall  be  considered  standard,  but  any 
asphalt  with  properties  differing  somewhat  from  the  above  can  be 
used  if  satisfactory  to  the  City  Engineer. 

e.  Heavy  Petroleum  Oil — The  oil  used  in  the  manufacture  of 


f ' 

PLANS  AND  SPECIFICATIONS.  390 

asphaltic  cement  as  hereinafter  described  shall  be  a  petroleum 
from  which  the  lighter  oils  have  been  removed  by  distillation  with- 
out cracking  until  the  oil  has  a  specific  gravity  of  from  18°  to  22° 
Beaume  and  the  following  properties: 

1.  Flash-test  not  less  than  300°  F.     (The  flash-test  shall  be 
taken  in  a  New  York  State  closed  oil-tester.) 

2.  Fire-test  not  less  than  350°  F. 

3.  No  appreciable  amount  of  light  oils  or  matter  volatile  under 
250°  F. 

4.  Distillate  at  400°  F.  for  thirty  hours,  less  than  10  per  cent. 
(The  distillate  shall  be  made  with  about  50  grams  of  oil  in  a  small 
glass  retort  provided  with  a  thermometer  and  packed  in  asbestos.) 

5.  It  shall  be  free  from  foreign  matter  and  coke. 

/.  Asphaltic  Cement. — Asphaltic  cement,  manufactured  from 
refined  asphalt  and  heavy  petroleum  oil  or  other  approved  flux> 
agreeing  in  composition  and  properties  with  those  described  in  the 
foregoing  paragraph,  shall  be  prepared  in  the  following  manner: 

To  the  melted  asphalt  at  a  temperature  of  not  over  325° 
Fahrenheit,  the  oil,  after  having  been  heated  to  at  least  250° 
Fahrenheit,  is  to  be  added  in  suitable  proportions  to  produce  an 
asphaltic  cement  equal  to  the  submitted  sample.  As  soon  as  the 
flux  has  begun  to  be  added,  suitable  agitation,  by  means  of  an 
air-blast  or  other  acceptable  appliances,  shall  commence  and  be 
continued  until  a  homogeneous  cement  is  produced.  The  appli- 
ances for  agitation  shall  be  such  as  to  accomplish  this  in  ten 
hours,  during  which  time  the  temperature  shall  be  kept  at  from 
250°  to  350°  Fahrenheit,  and  no  higher.  If  the  cement  then  ap- 
pears homogeneous  and  free  from  lumps  and  inequalities,  it  may 
be  used.  Should  it  not  prove  homogeneous,  such  deficiencies  as 
may  exist  shall  be  corrected  by  the  addition  of  hot  flux  or  melted 
asphalt  in  the  necessary  proportions.  Asphaltic  cement  shall  ful- 
fil tests  enumerated  under  heavy  petroleum  oil.  When  asphalt 
cement  is  kept  in  storage,  it  must  be  thoroughly  agitated  when 
used,  as  must  all  dipping-kettles  while  in  use.  Samples  of  asphaltic 
cement  and  of  the  flux  shall  be  supplied  to  the  City  Engineer  or 
his  approved  agents  when  required,  in  suitable  tin  boxes  and  cans, 
and  he  shall  have  access  to  all  branches  of  the  work  at  any  time. 
Should  ft  be  determined  by  experience  that  the  asphaltic  cement 


400        STREET  PAVEMENTS  AND  PAVING  MATERIALS, 

as  submitted  does  not  produce  a  satisfactory  pavement,  its  propor- 
tions may  be  changed  with  the  approval  of  the  City  Engineer. 

g.  Finely  Powdered  Mineral  Matter. — The  powdered  mineral 
matter  must  be  of  such  degree  of  fineness  that  the  whole  of  it  will 
pass  a  30-mesh  screen,,  and  at  least  seventy-five  per  cent  a  100- 
mesh  screen. 

h.  Sand. — The  sand  in  use  shall  be  hard-grained,  moderately 
sharp  and  clean,  not  containing  more  than  one  per  cent  of  hydro- 
silicate  of  aluminum.  On  sifting,  the  whole  of  it  shall  pass  a  10- 
mesh  screen,  twenty  per  cent  shall  pass  an  80-mesh  screen,  and  at 
least  seven  per  cent  shall  pass  a  100-mesh  screen. 

The  material  complying  with  the  above  specifications  shall  be 
mixed  in  the  following  proportions  by  weight: 

Asphaltic  cement from  15  to  18 

Sand  from  80  to  67 

Pulverized  mineral  matter from     5  to  15 

The  proportions  of  materials  used  will  depend  upon  the  charac- 
ter, and  will  be  determined  by  the  City  Engineer;  but  the  per- 
centage of  bitumen  flux  in  any  paving  mixture  soluble  in  carbon 
bisulphide  shall  not  be  less  than  nine  nor  more  than  twelve  per 
cent.  If  the  proportions  of  the  mixture  are  varied  in  any  manner 
from  those  specified,  the  mixture  will  be  condemned,  its  use  will 
not  be  permitted,  and,  if  already  placed  on  the  street,  it  must  be 
removed  and  replaced  by  proper  materials  at  the  expense  of  the 
Contractor. 

The  sand  and  asphaltic  cement  shall  be  heated  separately  to 
about  300°  Fahrenheit.  The  pulverized  carbonate  of  lime,  granite, 
or  quartz  while  cold  shall  be  mixed  with  the  hot  sand  in  the  re- 
quired proportions,  and  then  mixed  with  the  asphaltic  cement,  at 
the  required  temperature  and  in  the  proper  proportion,  in  a  suit- 
able apparatus,  so  as  to  effect  a  thoroughly  homogeneous  mixture. 
Sand-boxes  and  asphalt  gauges  must  be  weighed  in  the  presence 
of  inspectors  as  often  as  may  be  desired. 

i.  Laying  the  Pavement. — The  pavement  mixture  prepared  in 
the  manner  thus  indicated  must  be  brought  to  the  ground  in  carts 
at  a  temperature  of  not  less  than  250°  Fahrenheit;  and  if  the 
temperature  of  the  air  is  less  than  50°  Fahrenheit,  the  Contractor 


PLANS  AND  SPECIFICATIONS.  401 

must  prepare  suitable  apparatus  in  order  to  maintain  the  proper 
temperature  of  the  mixture. 

It  shall  then  be  thoroughly  spread  by  means  of  hot  iron  rakes 
in  such  manner  as  to  give  a  uniform  and  regular  grade,  to  such 
depth  that  after  having  received  its  ultimate  compression  it  will 
have  a  net  thickness  of  two  inches. 

The  surface  will  then  be  compressed  by  hand-rollers,  after 
which  a  small  amount  of  hydraulic  cement  will  be  swept  over  it, 
and  it  will  then  be  thoroughly  compressed  by  a  steam-roller  weigh- 
ing not  less  than  five  tons,  followed -by  one  of  not  less  than  ten 
tons,  the  rolling  being  continued  as  long  as  it  makes  any  impres- 
sion on  the  surface. 

In  order  to  make  the  gutters,  which  are  consolidated  but  little 
by  traffic,  entirely  impervious  to  water,  a  width  of  twelve  inches 
next  the  curb  must  be  coated  with  hot  asphaltic  cement  and 
smoothed  with  hot  smoothing-irons,  which  operations  must  com- 
pletely saturate  the  pavement  to  a  depth  of  one  inch  with  an 
excess  of  asphalt.  This  must  immediately  follow  the  rolling  before 
the  surface  has  become  cold  or  covered  with  any  extraneous  matter. 

j.  Liquid  Asphalt. — Should  a  liquid  asphalt  or  other  softening 
agent  be  used  as  a  substitute  for  a  portion  or  for  all  of  the  petro- 
leum residuum  in  making  the  asphaltic  cement,  such  liquid  asphalt 
or  other  softening  agent  must  fulfil  the  tests  enumerated  in  para- 
graph e  for  heavy  petroleum  oil;  it  must  contain  not  less  than 
ninety-five  per  cent  of  bitumen,  and  its  acidity  in  terms  of  caustic 
potash  must  not  exceed  two  per  cent.  The  softening  agent  shall 
be  such  that  when  added  to  the  refined  asphalt  in  proper  propor- 
tion it  will  produce  an  asphaltic  cement  having  essentially  the  same 
consistency  and  the  same  properties  as  that  made  of  refined  asphalt 
•and  heavy  petroleum  oil,  as  hereinbefore  described,  or  properties 
that  shall  be  considered  and  accepted  by  the  City  Engineer  as 
equivalent  or  superior  thereto. 

k.  Rock  Asphalt. — Should  any  of  the  rock  asphalts  be  used,  the 
material  shall  be  a  natural  bituminous  limestone  and  shall  be  pre- 
pared and  laid  in  the  following  manner: 

The  lumps  of  rock,  after  being  mixed  in  the  proper  propor- 
tions, shall  be  finely  crushed  and  pulverized,  and  the  powder  shall 
then  be  passed  through  a  20-mesh  sieve.  Nothing  whatever  shall 


402        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

be  added  to  or  taken  from  the  powder  obtained  by  grinding  the 
bituminous  rock.  The  powder  shall  contain  from  9  to  12  per  cent 
of  natural  bitumen. 

This  powder  shall  be  heated  in  a  suitable  apparatus  to  200°  or 
250°  Fahrenheit,  and  must  be  brought  to  the  ground  at  a  tempera- 
ture of  not  less  than  180°  F.,  in  carts  made  for  the  purpose,  and 
then  carefully  spread  on  the  concrete  foundation  prepared  as  speci- 
fied for  refined  asphalt  pavement,  to  such  a  depth  that  after  having 
received  its  ultimate  compression  it  will  have  a  thickness  of  2^ 
inches.  The  surface  shall  be  rendered  perfectly  even  by  tamping,, 
smoothing,  and  rolling  with  heated  appliances  of  approved  design. 
After  the  completion  of  the  work,  and  whenever  the  City  Engineer 
shall  so  direct,  the  surface  of  the  pavement  must  be  sprinkled  with 
clean,  sharp  sand.  If  rock  asphalts  are  used,  the  gutters  need  not 
be  saturated  with  asphaltic  cement. 

/.  General  Requirement. — The  asphalt  for  use  under  this  con- 
tract shall  be  one  agreeing  in  composition  and  properties  with  that 
described  in  a  foregoing  section,  or  one  having  composition  and 
properties  which  shall  be  considered  and  accepted  as  equivalent 
or  superior  thereto  by  the.  City  Engineer;  but  whatever  may  be 
the  character  of  the  asphalt  used  in  the  manner  of  manipulation 
and  laying,  the  pavement  obtained  must  be  the  same  as  or  equal  to 
that  resulting  from  the  use  of  the  standard  mixture  described  in 
Section  h  and  shall  conform  to  the  following  general  requirements: 

The  pavement  when  laid  shall  not  be  so  soft  as  to  be  unfit  for 
travel  on  the  hottest  days  of  summer,  nor  so  hard  as  to  disin- 
tegrate from  the  effects  of  frost.  When  laid  it  shall  be  equal  in 
consistency,  surface,  durability,  and  other*  properties  to  the  stand- 
ard pavement  made  as  hereinbefore  described.  It  shall  contain  no 
water,  nor  an  appreciable  amount  of  light  oils,  nor  matter  volatile 
at  a  temperature  under  250°  Fahrenheit.  It  shall  yield,  when  ex- 
tracted with  bisulphide  of  carbon  and  after  evaporation  of  the 
solvent,  not  less  than  nine  nor  more  than  twelve  per  cent  of  sub- 
stance which  shall  have  the  same  properties  as  the  substance  ex- 
tracted in  the  same  way  from  the  above-mentioned  pavement  made 
from  refined  asphalt,  heavy  petroleum  residuum,  and  mineral 
matter  in  accordance  with  the  foregoing  specification,  or  proper- 
ties which  shall  be  considered  and  accepted  as  equivalent  or  su- 


PLANS  AND  SPECIFICATIONS.  403 

perior  thereto  by  the  City  Engineer.  The  extracted  bituminous 
matter  shall  have  a  fire-test  of  350°  Fahrenheit,  and  shall  not 
possess  any  marked  acidity  to  caustic  potash.  The  mineral  matter 
which  it  contains  shall  be  the  same  or  equivalent  in  nature  and 
condition  to  that  prescribed  in  the  preparation  of  the  standard 
pavement  hereinbefore  described  (at  least  fifteen  per  cent  of  which 
mineral  matter  shall  pass  a  100-mesh  (per  lineal  inch)  sieve),  except 
in  case  of  the  use  of  rock  asphalt,  when  the  mineral  matter  shall 
be  that  which  occurs  in  the  natural,  product. 

m.  Xo  asphalt  shall  be  laid  during  wet.  weather,  nor  unless 
the  surface  of  the  concrete  is  perfectly  dry.  All  materials  as  well 
as  the  plant  and  methods  of  manufacture  shall  be  subject  at  all 
times  to  the  inspection  and  approval  of  the  City  Engineer  or  of 
such  engineer  and  inspectors  as  may  be  in  charge  of  the  work. 

Granite  Pavement. 

(14)  a.  Description  of  Paving -blocks. — Stone  blocks  shall  be 
of  granite  of  a  durable,  sound,  and  uniform  quality,  each  stone 
measuring  not  less  than  eight  inches  nor  more  than  twelve  inches 
in  length,  not  less  than  three  and  one-half  nor  more  than  four  and 
one-half  inches  in  width,  and  not  less  than  seven  nor  more  than 
eight  inches  in  depth,  and  the  stone  shall  be  of  the  same  quality 
as  to  hardness,  color,  and  grain.  No  outcrop,  soft,  brittle,  or 
laminated  stone  will  be  accepted.  Around  car-tracks  and  man- 
holes the  blocks  may  be  of  other  dimensions  than  above  described 
when  specially  so  directed  by  the  Chief  Engineer.  No  stone  shall 
l>e  laid  between  the  rails  of  any  car-track  that  is  more  than  ten 
Inches  long. 

The  stone  from  each  quarry  shall  be  piled  and  laid  together 
in  separate  sections  of  the  work,  and  in  no  case  shall  the  stones 
from  different  quarries  be  mixed,  or  stone  of  different  widths  be 
laid  in  the  same  course  except  on  curves. 

The  blocks  are  to  be  rectangular  on  the  tops  and  sides,  uni- 
form in  thickness,  split  and  dressed  so  as  to  form,  when  laid,  close 
joints,  with  fair  and  true  surfaces,  free  from  bunches. 

All  blocks  measuring  in  thickness  from  three  and  one-half  to 
four  inches,  inclusive,  shall  be  considered  as  one  class,  and  all 
blocks  four  up  to  and  including  those  four  and  one-half  inches 


404        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

thick  shall  be  considered  as  in  another  class.  These  two  classes 
must  be  kept  apart,  and  brought  upon  and  laid  in  separate  sections, 
of  the  work. 

b.  Laying  the  Pavement. — On  the  roadbed,  prepared  as  herein- 
before specified,  or  on  the  concrete  foundation  as  designated,  shall 
be  laid  a  bed  of  clean,  coarse  dry  sand,  to  such  depth  as  may  be 
necessary  to  bring  the  surface  of  the  pavement,  when  thoroughly 
rammed,  to  the  proper  grade. 

On  this  sand  bed  and  to  the  grade  and  crown  specified,  shall 
be  laid  the  stone  blocks  at  right  angles  to  the  line  of  the  street 
or  at  such  other  angle  as  may  be  directed.  ' 

Each  course  of  blocks  shall  be  laid  straight  and  regularly,  with 
the  longitudinal  or  end  joints  broken  by  a  lap  of  at  least  three 
inches. 

All  joints  shall  be  close  joints,  except  that  when  gravel  filling 
is  used,  the  joints  between  courses  shall  not  be  more  than  three- 
fourths  of  one  inch  in  width. 

c.  Sand  Foundation. — When  the   blocks   are   laid   on   a   sand 
foundation  they  shall  be  covered  to  within  three  courses  of  the 
pavers  with  sharp,  coarse  sand,  free  from  stones,  which  shall  be 
raked  until  all  the  joints  become  filled  therewith.    Each  course  of 
blocks  shall  then,  with  proper  tools,  be  set  up  perpendicular  to 
the  surface  of  the  street,  and  all  blocks  not  uniform  in  width  or 
properly  laid  shall  be  taken  out  and  proper  ones  set  in  their  places;, 
the  blocks  shall  then  be  thoroughly  rammed  to  a  firm,  unyielding- 
bed  of  uniform  surface  to  conform  to  the  grade  and  crown  of 
street.    No  ramming  shall  be  done  within  twenty  feet  of  the  work 
that  is  being  laid.    Whenever  the  pavement  for  as  great  a  distance 
as  may  be  deemed  desirable  shall  have  been  constructed  as  above 
described,  it  shall  be  covered  with  a  good  and  sufficient  second  coat 
of  clean,  sharp  sand,  and  shall  immediately  thereafter  be  thor- 
oughly rammed  until  the  work  is  made  solid  and  secure;    and  so- 
on  until  the  whole  of  the  work  embraced  in  this  agreement  shall 
have  been  well  and  faithfully  completed  in  accordance  with  these 
specifications.    This  second  coating  of  sand  shall  be  left  upon  the 
pavement  for  thirty  days.     At  the  end  of  that  time  the  sand 
shall  be  removed  and  the  pavement  cleaned  at  the  expense  of  the 
Contractor. 


PLANS  AND  SPECIFICATIONS.  405 

The  Contractor  shall  sprinkle  with  water  the  sand  placed  upon 
the  pavement  during  the  time  it  is  left  thereon,  as  may  be  directed 
by  the  Engineer  in  charge,  and  shall  then  comply  with  the  ordi- 
nances relating  to  the  dropping  of  dirt,  sand,  etc.,  in  the  city 
streets;  and  if  any  dirt,  sand,  etc.,  shall  be  dropped  upon  the  city 
streets,  said  streets  may  be  cleaned  up  as  often  as  may  be  deemed 
necessary  by  the  Commissioner,  and  the  expense  of  the  same  may 
be  deducted  from  any  sum  otherwise  due  the  Contractor. 

d.  Concrete  Foundation. — When  the  pavement  is  laid  on  a 
concrete  foundation,  the  blocks,  laid  as  above,  shall  be  covered  with 
clean,  hard,  dry,  and  hot  gravel  which  shall  have  been  artificially 
heated  and  dried  in  proper  appliances  placed  in  close  proximity  ta 
the  work,  and  brushed  in  until  all  the  joints  are  filled  within  three 
inches  of  the  top. 

The  gravel  must  be  entirely  free  from  sand  or  dirt  and  must 
have  passed  through  a  sieve  of  five-eighths-inch  mesh  and  been  re- 
tained by  one  of  three-eighths-inch  mesh. 

The  blocks  must  then  be  thoroughly  rammed,  and  the  ram- 
ming shall  be  repeated  until  they  are  brought  to  an  unyielding 
bearing  with  a  uniform  surface,  true  to  the  given  grade  and  crown. 
No  additional  gravel  shall  be  added  after  the  ramming  before  the 
first  pouring  of  the  cement. 

The  boiling  paving-cement,  heated  to  a  temperature  of  300° 
F.  and  of  the  composition  hereinafter  described,  shall  then  be 
poured  into  the  joints,  while  the  gravel  is  still  hot,  until  the  same 
are  filled  flush  with  the  top  of  the  gravel. 

Dry,  hot  gravel  of  proper  size,  which  shall  have  been  heated 
in  pans  especially  provided  for  the  purpose,  shall  then  be  poured 
into  the  joints  until  they  are  filled,  when  the  hot  paving-cement 
shall  be  again  poured  into  the  joints  until  they  are  filled  and  re- 
main full. 

The  appliances  for  heating  paving-cement  shall  be  sufficient  in 
number  and  of  such  efficiency  as  will  permit  the  pourers  to  closely 
follow  the  back-rammers.  All  joints  of  the  finally  rammed  pave- 
ment shall  be  filled  with  paving-cement  as  noted  above,  before  the 
cessation  of  work  for  the  day  or  any  other  cause. 

No  horse,  cart,  or  vehicle  of  any  description  shall  be  permitted 
to  stand  on  or  pass  over  the  pavement  until  the  joints  have  been 


406        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

finally  poured  with  cement  as  above,  and  the  same  has  had  time 
to  harden. 

e.  Paving-cement. — The  paving-cement  to  be  used  in  filling  the 
joints  shall  be  composed  of  twenty  parts  of  refined  Trinidad  or 
other  approved  asphalt  and  three  parts  of  residuum  oil  mixed  with 
one  hundred  parts  of  coal-tar  pitch,  which  shall  be  obtained  from 
the  direct  distillation  of  coal-tar,,  and  shall  be  the  residuum  there- 
from,, and  shall  be  such  as  is  ordinarily  known  as  number  four 
at  the  manufactory;  all  proportions  to  be  determined  by  weight. 
It  shall  be  delivered  in  lots  at  least  one  week  before  being  used, 
that  the  necessary  analysis  and  examination  may  be  made.  The 
Contractor  must  also  furnish  a  certificate  from  the  manufacturer 
or  refiner  that  the  materials  are  of  the  kind  specified.  The  coal- 
tar,  oil,  and  asphalt  must  be  heated  and  mixed  in  the  proportions 
named  by  weight  on  the  work  as  needed  for  immediate  use. 

Medina  Sandstone  Pavement. 

(15)  a.  Blocks. — Paving-blocks  shall  consist  of  the  best  quality 
of  Medina  sandstone,  and  shall  not  be  less  than  three  and  one- 
fourth  nor  more  than  five  inches  thick,  and  not  less  than  six  nor 
more  than  six  and  one-half  inches  deep,  and  from  eight  to  thirteen 
inches  long.  The  stones  to  have  parallel  sides  and  ends,  with  right- 
angle  joints;  all  roughness  and  points  of  stones  to  be  broken  off, 
so  that  when  set  in  place  they  shall  have  tight  joints  for  a  dis- 
tance of  at  least  three  and  one-half  inches  from  the  top  down;  the 
•area  of  the  bottom  of  any  stone  to  be  not  less  than  three-fourths  of 
the  area  of  the  top.  Top  to  have  a  smooth,  even  surface. 

Paving-blocks,  as  here  referred  to,  shall  be  understood  to  mean 
Hocks  of  Medina  sandstone,  prepared  in  a  proper  manner  for 
dressed-block  paving,  by  nicking  and  breaking  the  stones  from 
larger  blocks,  as  is  done  at  the  quarries  where  such  blocks  are 
usually  prepared,  and  not  made  by  redressing  or  selecting  from 
common  stone  paving  material.  Stones  to  be  flat  and  even  at 
bottom,  which  shall  be  parallel  with  the  top  surface,  with  both  top 
and  bottom  of  stones  at  right  angles  to  at  least  one  end  of  the 
stone,  so  as  to  set  squarely  and  firmly  in  place  without  the  use  of 
a  paving-hammer. 


- 

PLANS  AND  SPECIFICATIONS.  407 

~b.  All  paving-blocks,  before  being  placed  upon  the  streets 
where  they  are  to  be  laid,  shall  be  properly  assorted,  and  all  stones 
of  greater  or  less  dimensions  than  above  specified  shall  be  rejected; 
all  acceptable  stones  shall  be  gauged  as  to  thickness  into  at  least 
three  classifications,  and  each  class  marked  with  oil  paint  in  the 
following  order,  to  wit: 

Class  No.  1  to  embrace  all  blocks  from  three  and  one-fourth  to 
and  including  three  and  one-half  inches  in  thickness;  Class  No.  2 
to  embrace  all  blocks  from  three  and  three-fourths  to  and  in- 
cluding four  and  one-fourth  inches  in  thickness;  Class  No.  3  to 
embrace  blocks  from  four  and  one-half  to  and  including  five  inches 
in  thickness.  Blocks  in  Class  No.  1  to.  be  marked  with  red  paint; 
those  in  Class  No.  2  with  blue  paint;  and  those  in  Class  No.  3 
with  black  paint.  Each  and  every  block  shall  receive  its  proper 
mark,  in  order  clearly  to  designate  to  which  class  the  same  be- 
longs. 

All  such  assorting,  gauging,  and  marking  shall  be  done  under 
the  direction  and  to  the  satisfaction  of  the  City  Engineer  before 
being  delivered  upon  the  street;  but  it  is  distinctly  understood  that 
such  inspection  shall  not  prevent  such  further  inspection  and 
assorting  as  the  City  Engineer  may  deem  necessary  to  obtain  good 
work. 

The  Contractor  shall  at  all  times  furnish  at  his  own  expense 
a  sufficient  number,  in  the  judgment  of  the  City  Engineer,  of 
careful  and  proper  persons  to  properly  do  such  classifying  and 
marking  of  the  blocks  as  here  specified. 

c.  After  the  blocks  have  been  classified  and  marked  as  above 
specified,  they  shall  be  kept  separate  and  distinct  in  hauling  to 
and  piling  upon  the  street;  each  wagon  loaded  with  a  particular 
class  of  blocks  shall  be  unloaded  only  at  places  on  the  street  where 
stones  of  a  like  class  are  to  be  unloaded;  blocks  of  the  different 
classes  are  to  be  placed  on  different  sides  of  the  street  or  in 
separate  piles  upon  the  same  side,  as  the  City  Engineer  shall  di- 
rect. 

In  wheeling  or  placing  the  blocks  in  the  beds  for  laying,  the 
same  care  shall  be  observed  not  to  injure  the  surface  of  any  bed 
or  foundation  after  the  same  has  been  properly  prepared  for  the 
blocks,  and  also  to  keep  the  classes  distinct  and  separate  from 


408        STREET  PAVEMENTS  AND   PAVING  MATERIALS. 

each  other;  but  if  from  any  cause  the  classes  of  blocks  have  be- 
come mixed  up  in  the  beds  before  laying,  or  are  so  found  after 
being  placed  in  the  pavement,  or  the  surface  of  the  foundation 
disturbed,  the  City  Engineer  may  order  all  such  blocks  removed 
from  the  beds  or  work,  and  reasserted,  gauged,  and  marked,  and 
the  foundation  repaired,  as  heretofore  specified,  and  at  the  expense 
of  the  Contractor. 

It  is  understood  that  all  such  classifying  and  marking  of 
the  blocks  is  for  the  purpose  of  assuring  more  uniformity  in  the 
construction  of  the  pavement,  and  by  placing  before  the  paver 
blocks  of  more  uniform  depth  and  thickness  to  aid  in  the  progress 
of  his  work. 

d.  Stones  are  to  be  set  tight  together,  in  uniform  rows,  break- 
ing joints  at  least  two  inches  and  resting  against  stones,  in  the 
same  and  the  adjoining  course;   those  of  the  same  class  and  thick- 
ness to  be  placed  together  in  the  same  row;  rows  of  similar  thick- 
ness to  be  placed  together,  and  set  directly  upon  a  cushion  of  one 
inch  of  sand  spread  upon  the  concrete  foundation;    no  gravel  or 
sand  to  be  placed  on  top  or  between  the  stones  as  laid.   Stones  to  be 
set  perpendicular  to  the  grade,  and  in  right-angle  courses  across, 
the  street,  except  at  street  and  alley  intersections,  where  the  courses 
are  to  be  set  at  such  angle  as  the  City  Engineer  shall  direct.    Upon 
the  completion  of  every  fourth  course  or  oftener,  as  the  City  En- 
gineer may  direct,  the  course  shall  be  driven  together  and  straight- 
ened by  the  use  of  a  heavy  sledge,  and  wood  block  placed  against 
the  stones  as  directed.     The  pavement  shall  always  be  laid  by  the 
paver  standing  upon  the  upper  side  of  his  work;    the  pavement 
shall  then  be  subjected  to  the  following  treatment  by  the  Con- 
tractor, and  in  such  order  and  to  such  extent  as  the  City  Engineer 
shall  direct: 

e.  The  paving  to  be  thoroughly  rammed  by  courses,  three  or 
more  times,  besides  the  first  and  final  surfacing,  as  may  be  di- 
rected,  with   a  paver's  rammer,   weighing  not   less   than   eighty 
pounds,  no  iron  of  any  kind  being  allowed  on  its  lower  face  to  come 
in  contact  with  the  paving.     The  pavement  to  be  surfaced  up  by 
using  a  long  straight-edge,  and  when  complete  to  conform  to  the 
true  grade  and  crown  of  the  roadway,  as  directed  by  the  Chief 
Engineer.     The  first  ramming  of  the  pavement,  if  so  ordered,  to> 


PLANS  AND  SPECIFIC A2 IONS.  409 

"be  done  by  one  man,  using  a  hand-rammer  of  not  more  than  36 
square  inches  face  and  weighing  from  25  to  40  pounds,  as  ordered. 
Such  first  ramming  to  be  done  only  on  such  paving-stones  as  may 
project  above  the  general  surface  of  the  other  stones,  for  the  pur- 
pose of  evening  the  surface  of  the  pavement  as  first  laid  before 
using  the  heavy  rammer,  as  heretofore  specified. 

The  pavement  after  having  been  laid  and  rammed,  or  during  the 
process  of  ramming,  shall  be  thoroughly  rolled  to  the  satisfaction 
of  the  City  Engineer. 

f.  The  pavement  after  ramming  and  rolling,  or  during  the 
process,  as  may  be  directed,  shall  be  thoroughly  sprinkled  or 
washed  with  water,  to  insure  the  thorough  bedding  of  the  blocks, 
leaving  the  joints  or  spaces  between  the  stones  their  full  depth. 

The  spaces  or  joints  shall  then  be  filled  with  a  concrete  com- 
position, consisting  of  either  paving-cement,  Portland  cement, 
Murphy  grout-filling,  or  such  other  composition  as  the  Director  of 
Public  Works  and  Chief  Engineer  may  order  or  approve,  and  shall 
be  mixed  and  used  in  the  following  manner: 

If  paving-cement  filling  is  used,  it  shall  consist  of  the  same 
composition  as  that  specified  under  Granite  Pavement. 

If  either  Portland  cement  or  Murphy  grout-filling,  or  both, 
are  ordered  or  permitted  to  be  used  on  the  street,  they  shall  be  of 
approved  quality  and  used  as  follows: 

The  Portland  cement,  if  used,  shall  consist  of  a  cement  which, 
in  the  opinion  of  the  City  Engineer,  is  equal  in  tenacity,  durability, 
and  hardness  to  the  best  American  Portland  cement. 

The  Murphy  cement,  if  used,  shall,  in  the  opinion  of  the  City 
Engineer,  consist  of  the  best  quality  of  that  material  made  by  John 
Murphy,  at  Columbus,  0. 

The  material,  whether  of  Portland  or  Murphy  cement,  shall  be 
fresh,  live  cement  and  finely  ground,  and  be  subject  to  the  tests 
and  approval  of  the  City  Engineer  before  being  used  on  the  work. 

The  cement  of  either  kind  used,  after  having  been  approved 
by  th'e  City  Engineer,  is  to  be  mixed  with  clean,  sharp  lake  sand, 
of  approved  quality,  in  the  proportion  of  one  to  one;  the  cement 
and  sand  to  be  thoroughly  mixed  together  dry  in  a  box  of  the  proper 
form  "and  capacity,  and  then  only  a  sufficient  amount  of  water 


410        STREET  PAVEMENTS  AND  PAVING  MATERIALS, 

added  to  make  the  grout  of  the  proper  fluidity  when  thoroughly 
stirred. 

The  grout  shall  be  prepared  only  in  small  quantities  at  a  time, 
and  shall  be  stirred  rapidly  and  constantly  in  the  box  while  being 
applied  to  the  pavement,  and  no  settlings  or  residue  will  be  allowed 
to  be  used. 

The  grout-filling  shall  be  transferred  to  the  pavement  in  hand- 
scoops,  or  in  such  other  way  as  the  Engineer  may  think  most  ad- 
vantageous and  best  for  the  work,  and  shall  then  be  rapidly  swept 
into  the  joints  of  the  pavement  with  proper  brooms. 

Unless  otherwise  directed,  the  filling  is  to  be  done  by  two 
applications  of  the  grout;  the  first  one-third  in  depth  from  the 
bottom  of  the  space  to  be  filled,  with  the  grout  somewhat  thinner 
than  required  for  the  remaining  two-thirds;  the  remainder  of  the 
spaces  is  then  to  be  filled  with  the  thicker  grout,  ajid  if  necessary 
refilled  until  the  joints  will  remain  full  to  the  top;  the  stones  to 
be  well  wet,  as  directed,  before  the  grout  is  applied. 

All  the  teams  and  wagon  traffic,  and  all  wheeling  in  barrows, 
except  on  planks,  to  be  rigidly  prohibited  on  the  pavement  for  one 
week  after  the  grout  is  applied,  or  until,  in  the  opinion  of  the 
Engineer,  it  has  become  thoroughly  set  and  hardened,  so  that  the 
bond  will  not  be  broken  by  traffic  over  the  pavement. 

g.  The  surface  of  the  paving,  when  completed  as  above,  shall, 
when  directed,  be  covered  with  a  half-inch  top  dressing  of  clean, 
coarse  sand,  or  gravel  of  approved  quality,  which,  with  all  accumu- 
lations, shall  afterwards  be  removed  from  the  pavement  and  from 
all  new  or  rebuilt  catch-basins,  by  or  at  the  expense  of  the  Con- 
tractor, at  such  time  before  the  final  acceptance  of  the  work,  as  the 
Engineer  shall  direct,  and  as  hereinafter  specified. 

Brick  Pavements. 

(16)  a'  Brick. — All  brick  shall  be  of  the  best  quality  of  vitri- 
fied paving-brick  made  of  shale  or  fire-clay,  repressed  and  especially 
burned  for  street-paving  purposes.  They  shall  not  be  more  than 
3x4x9  inches  nor  less  than  2£  x  4  x  8-|  inches  in  size;  but  only 
one  size  or  make  shall  be  used  in  any  single  contract.  They  shall 
be  hard,  tough,  strong,  and  non-absorbent  of  water,  and  shall  be 


PLANS  AND  SPECIFICATIONS.  411 

tested  under  the  conditions  prescribed  by  the  National  Brick 
Manufacturers'  Association  for  paving-brick.  They  shall  be 
rectangular,  with  parallel  sides  and  straight  edges,  uniform  in 
size  and  texture  and  free  from  cracks,  bunches,  or  defects  of  any 
kind,  and  equal  in  all  cases  to,  and  from  the  same  place  as,  the 
sample  submitted  with  the  bid. 

b.  Laying  the  Pavement. — On  the  concrete  foundation  shall  be 
laid  a  bed  of  clean,  coarse,  dry  sand  to  such  depth  as  may  be  neces- 
sary to  bring  the  surface  of  the  pavement,  when  thoroughly 
rammed  or  rolled,  to  the  proper  grade.  The  sand  cushion  shall 
be  brought  to  the  exact  form  and  crown  by  means  of  a  template 
of  the  proper  shape,  resting  on  the  curbs,  or  with  one  end  on  the 
curb  and  the  other  on  a  scantling  imbedded  in  the  sand  at  the 
centre.  The  template  shall  be  drawn  forward  and  backward  im- 
mediately in  front  of  the  bricklaying,  so  that  the  sand  cushion 
shall  be  maintained  constantly  at  the  proper  crown. 

On  this  sand  bed  the  brick  shall  be  set  on  edge  at  right  angles 
to  the  curb-line,  except  at  intersecting  streets,  where  they  shall 
be  laid  at  such  angles  and  in  such  manner  as  the  Engineer  may 
direct. 

All  the  longitudinal  joints  must  be  broken  by  a  lap  of  half 
the  length  of  the  brick.  The  brick  shall  be  laid  in  close  contact 
with  each  other  by  skilled  workmen,  who  shall  stand  on  the  bricks 
already  laid,  and  in  no  case  shall  the  bed  of  sand  in  front  of  the 
pavement  be  disturbed  or  walked  upon  after  having  been  smoothed 
over  and  brought  to  the  exact  crown  and  grade. 

After  the  bricks  are  laid,  the  end  joints  are  to  be  made  close 
and  compact  by  the  use  of  a  steel  bar  applied  at  the  ends  next  the 
curbs. 

At  every  fourth  course,  or  as  often  as  directed,  the  bricks  are 
to  be  closed  up,  and  the  courses  straightened  in  a  satisfactory  man- 
ner. Nothing  but  whole  brick  shall  be  used,  except  in  starting  or 
finishing  a  course,  or  in  such  other  cases  as  may  be  specially 
directed  by  the  Engineer,  and  in  no  case  shall  less  than  one-half 
of  a  brick  be  used.  In  all  cases  the  end  joints  shall  be  made  close 
and  tight. 

The  cutting  and  trimming  of  bricks  shall  be  done  by  experi- 
enced men  and  proper  care  taken  not  to  check  or  fracture  the- 


412        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

part  to  be  used;  the  joints  all  to  be  at  right  angles  to  the  top  and 
sides. 

As  soon  as  the  block  between  any  two  intersecting  streets  shall 
have  been  laid,  the  brick  shall  be  thoroughly  wet  by  sprinkling 
with  a  hand-hose,  and  any  soft  bricks  which  may  be  thus  detected 
shall  be  taken  out  and  replaced  by  good,  hard  brick. 

c.  Rolling. — The   pavement   shall   then   be   swept   clean   with 
brooms  and  afterward  rolled  with  a  roller  weighing  not  less  than 
five  tons  till  all  brick  are  thoroughly  imbedded  in  the  sand  and 
brought  to  an  unyielding  bearing,  making  the  finished  surface  of 
the  pavement  smooth  and  even,  conforming  to  the  required  grade 
and  crown. 

All  bricks  that  may  be  broken  or  chipped  in  any  way  by  the 
rolling  shall  be  taken  out  and  replaced  with  perfect  ones. 

d.  Joints. — When    Portland-cement    joints    are    specified,    the 
surface  of  the  pavement,  after  rolling  as  above,  shall  be  thoroughly 
wet  and  grouted  with  a  mixture  of  equal  parts  of  the  best  American 
Portland  cement,  as  heretofore  required,  and  fine,  sharp,  washed 
sand,  mixed  with  sufficient  water  to  run  freely;    the  grout  to  be 
poured  over  the  surface  of  the  pavement  and  well  swept  into  the 
joints  with  stiff  brooms  until  no  further  settlement  is  apparent 
and  the  cement  filling  remains  flush  with  the  top  of  the  bricks. 
When  required  a  thin  layer  of  clean  sand  shall  thereafter  be  spread 
upon  the  pavement  and  the  street  shall  remain  closed  for  seven 
days,  or  longer  if  so  deemed  necessary  by  the  City  Engineer,  after 
which  it  shall  be  thrown  open  to  travel. 

e.  If  sand  joints  are  specified,  the  pavement  when  perfectly 
dry  shall  be  covered  with  a  thin  layer  of  clean,  dry,  fine  sand 
(dried  upon  the  street  by  artificial  means,  if  necessary,  immediately 
before  using),  which  shall  be  swept  into  all  the  joints  by  stiff 
brooms.    The  surface  shall  then  be  thoroughly  rolled  with  a  roller 
weighing  not  less  than  five  tons,  after  which  a  fresh  coating,  treated 
as  before,  shall  be  applied,  and  again  swept  into  the  joints.     A 
coating  of  one-half  inch  of  the  same  sand,  but  which  need  not  be 
heated,  shall  then  be  spread  over  the  surface,  and  the  street  shall 
be  thrown  open  to  travel. 

/.  When  paving-cement  is  specified  for  a  filler,  the  joints  shall 
be  slowly  poured  full  with  a  paving  composition  as  described  in 


PLANS  AND  SPECIFICATIONS.  413 

section  e  under  Granite  Pavement,  heated  to  a  temperature  of  300° 
F.  in  such  a  manner  as  to  cover  the  surface  of  the  brick  with  as 
little  pitch  as  possible.  After  this  first  pouring  has  been  allowed 
to  settle  away,  but  not  to  become  cool,  the  joints  shall  again  be 
poured  until  they  are  full  and  remain  full.  The  entire  surface  of 
the  pavement  shall  then  be  covered  with  one-half  inch  of  clean, 
perfectly  dry  sand.  The  sand  shall  be  left  on  the  pavement  until 
ordered  removed  by  the  Engineer,  when,  if  any  appreciable  amount 
of  pitch  still  remains  on  the  brick,  they  shall  be  covered  with  sand 
-as  before,  the  same  to  be  removed  when  directed  by  the  Engineer 
in  charge.  The  entire  operation  of  pouring  pitch  and  spreading 
the  sand  is  done  only  when  the  pavement  is  entirely  dry,  and  when 
the  work  is  done  in  cold  weather,  only  during  the  warmest  portion 
of  the  day. 

Asphalt-block  Pavement. 

(17)  a.  Blocks. — The  size  of  the  blocks,  must  be  four  inches 
^vvide,  three  inches  deep,  and  twelve  inches  long,  and  a  variation  of 
one-quarter  of  an  inch  from  these  dimensions  will  be  sufficient 
ground  for  rejecting  any  block. 

The  blocks  must  be  composed  of  the  following  materials: 

Paving-cement 10  to  14  parts 

Crushed- trap  rock 90  to  86       " 

The  paving-cement  must  be  made  from  steam-refined,  Trinidad 
Lake,  or  other  equally  good  asphaltum,  and  heavy  petroleum  oil 
free  from  all  impurities  and  brought  to  a  specific  gravity  of  from 
18  to  22  Beaume  and  a  fire-test  of  250°  Fahrenheit. 

Said  cement  must  be  composed  of  one  hundred  parts  of  pure 
asphaltum  and  eight  to  ten  parts  of  petroleum  oil. 

1).  Laying. — Upon  the  surface  of  this  concrete  foundation  shall 
be  spread  a  layer  of  cement  mortar  one-half  inch  in  thickness, 
which  shall  bring  the  thickness  of  the  complete  foundation  up 
to  five  inches.  This  mortar  surface  shall  be  composed  of  a  slow- 
setting  Portland  cement  and  clean,  sharp  sand  free  from  pebbles 
over  one-quarter  inch  in  diameter,  and  mixed  in  the  proportion  of 
one  part  of  cement  to  four  parts  of  sand.  This  mortar  top  shall  be 


414        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

"  struck  "  to  a  true  surface  exactly  parallel  to  the  finished  pave- 
ment and  three  inches  below  it,  in  the  following  manner: 

On  the  surface  of  the  concrete  shall  be  set  strips  of  wood 
four  inches  wide  by  one-quarter  inch  thick,  and  of  a  length  equal 
to  the  width  or  half  the  width  of  the  street  if  practicable;  or 
strips  of  steel  four  inches  wide  by  one-eighth  or  three-sixteenths 
inch  thick  and  of  a  convenient  length  may  be  used.  These  strips 
must  be  carefully  set  from  curb  to  curb  to  the  exact  crown  of  the 
street  and  imbedded  throughout  their  length  in  mortar,  so  that  the 
top  surface  of  the  strips  shall  be  three  inches  below  the  grade  of 
the  finished  pavements.  An  iron-shod  straight-edge  or  "  striker  "' 
shall  be  used  on  two  sets  of  strips,  set  as  described  above,  ten  or 
twelve  feet  apart,  to  strike  the  mortar  top  to  a  true  and  even 
surface.  As  soon  as  a  bed  has  been  struck  up,  one  set  of  strip* 
shall  be  taken  up  and  carefully  filled  with  mortar  with  a  trowel. 

Upon  this  mortar  surface  the  blocks  shall  be  immediately  laid 
with  close  joints. 

The  blocks  must  be  laid  by  the  pavers  standing  upon  the  blocks 
already  laid,  and  not  upon  the  bed  of  mortar. 

The  blocks  are  to  be  laid  at  right  angles  with  the  line  of  the- 
street,  with  such  crown  as  the  Engineer  may  direct;  each  course 
of  blocks  to  be  of  a  uniform  width  and  depth,  and  so  laid  that  all 
longitudinal  joints  shall  be  broken  by  a  lap  of  at  least  four  inches 
and  the  surface  present  a  smooth  and  uniform  appearance,  with 
proper  grade  and  crown. 

When  thus  laid  the  blocks  will  be  immediately  covered  with 
clean,  fine  sand,  entirely  free  from  any  loam  or  earthy  matter, 
perfectly  dry,  and  screened  through  a  sieve  or  screen  having  not  less 
than  twenty  meshes  to  the  inch.  This  sand  shall  be  swept  over 
the  surface  until  the  joints  are  all  filled. 

The  sand  as  above  described  will  be  allowed  to  remain  on  the 
pavement  not  less  than  thirty  days,  or  for  such  a  time  as  the  action 
of  the  traffic  on  the  street  shall  have  thoroughly  ground  the  top 
sand  into  all  the  joints. 

The  whole  operation  of  laying  the  blocks  and  cutting  in  at  the 
curb  shall  be  performed  upon  each  bed  struck  up,  before  the 
mortar  top  shall  have  begun  to  set.  As  soon  as  the  mortar  top 
shall  have  sufficiently  set,  the  street  may  be  opened  to  traffic. 


PLANS  AND  SPECIFICATIONS.  415 

In  case  of  car-tracks  in  the  streets  a  template  shall  be  used,  to 
run  on  the  rails,  to  strike  the  mortar  top  to  the  required  grade 
between  the  rails  of  the  car-track. 

(18)  In  case  any  curb,  flag,  paving,  trees,  fence  or  barrier,  or 
other  material  along  the  line  of  the  work  become  broken  or  in- 
jured by  the  Contractor  or  his  agents  during  the  progress  of  the 
work,  they  are,  if  required,  to  be  removed,  and  others  equally  as 
good  placed  in  their  stead,  at  the  expense  of  said  Contractor,  and 
to  the  satisfaction  of  the  Engineer. 

(19)  Should  any  sewer  manhole  or  catch-basin  heads  require 
raising  or  lowering  to  conform  with  the  proper  grade,  such  heads 
shall  be  so  raised  or  lowered  by  the  Contractor  at  his  expense.  Man- 
holes or  other  surface  work  of  any  corporation  will  be  adjusted  by 
the  company  or  corporation  owning  them  upon  notice  from  the  City 
Engineer. 

(20)  Clearing  Up. — All  surplus  materials,  earth,  sand,  rubbish, 
and  stones,  except  such  stones  as  shall  be  retained  by  the  order 
of  the  Engineer,  are  to  be  removed  from  the  line  of  the  work, 
block  by  block,  as  rapidly  as  the  work  progresses.     Unless  this  be 
done  by  the  Contractor  within  twenty-four  hours  after  being  noti- 
fied so  to  do,  to  the  satisfaction  of  the  City  Engineer,  the  same 
shall  be  removed  by  said  Engineer,  and  the  amount  of  the  expense 
thereof  shall  be  deducted  out  of  any  moneys  due  or  to  grow  due  to 
the  party  of  the  second  part  under  this  agreement. 

(21)  All  loss  or  damage  arising  out  of  the  nature  of  the  work 
to  be  done  under  this  agreement,  or  from  any  unforeseen  obstruc- 
tions or  difficulties  which  may  be  encountered  in  the  prosecution 
of  the  same,  or  from  the  action  of  the  elements,  or  from  incum- 
brances  on  the  line  of  the  work,  shall  be  sustained  by  the  said 
Contractor. 

In  case  any  injury  is  done  along  the  line  of  the  work  in  conse- 
quence of  any  act  or  omission  on  the  part  of  the  Contractor  or 
his  employees  or  agents  in  carrying  out  any  of  the  provisions  or 
requirements  of  this  contract,  the  Contractor  shall  make  such  re- 
pairs as  are  necessary  in  consequence  thereof,  at  his  own  expense 
and  to  the  satisfaction  of  the  City  Engineer;  and  in  case  of  failure 
on  the  part  of  the  Contractor  to  promptly  make  such  repairs,  thev 
may  be  made  by  the  City  Engineer,  and  the  expense  thereof  shall 


416        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

be  deducted  out  of  any  moneys  to  grow  due  or  to  be  retained  from 
the  party  of  the  second  part  under  this  contract. 

(22)  The  prosecution  of  the  work  shall  be  suspended  at  such 
times  and  for  such  periods  as  the  City  Engineer  may  from  time 
to  time  determine;  no  claim  or  demand  shall  be  made  by  the  Con- 
tractor for  such  damages  by  reason  of  suc'h  suspensions  in  the 
work,  but  the  period  of  such  suspensions  to  be  determined  in  writ- 
ing by  the  said  Engineer  will  be  excluded  in  computing  the  time 
hereinafter  limited  for  the  completion  of  the  work.     During  such 
suspension   all   materials   delivered  upon   but   not  placed   in  the 
work  shall  be  neatly  piled  or  removed  so  as  not  to  obstruct  public 
travel. 

(23)  Whenever  the  word  "  Contractor  "  or  a  pronoun  in  place 
of  it  is  used  in  this  contract,,  the  same  shall  be  considered  as  re- 
ferring to  and  meaning  the  party  or  parties  signing  the  contract  or 
his  authorized  agent. 

(24)  The  work  s'hall  be  commenced  on  such  day  and  at  such 
point  or  points  as  the  City  Engineer  shall  designate,  and  progress 
therewith  so  as  to  be  fully  completed  in  accordance  with  this  agree- 
ment, on  or  before  the  expiration  of  -         -  working  days. 

(25)  Damages  for  Non-completion. — If  the  Contractor  shall  fail 
to  complete  his  contract  within  the  time  specified,  the  City  En- 
gineer shall  make  a  careful  estimate  of  the  value  of  the  work  to 
be  performed  at  the  expiration  of  the  contract  time.     When  the 
work  shall  be  finally  complete  the  said  Engineer  shall  deduct  from 
the  final  estimate,  as  liquidated  damages,  'an  amount  equal  to  one- 
half  of  one  per  cent  of  the  value  of  such  uncompleted  work  ob- 
tained as  above  for  each  working  day  in  excess  of  the  time  specified 
in  the  contract,  provided  that  the  amount  charged  shall  not  be 
less  than  the  actual  increased  cost  of  inspection. 

(26)  If  at  any  time  any  overseer  or  workman  employed  by  the 
Contractor  shall  be  declared  by  the  Engineer  to  be  unfaithful  or 
incompetent,  the   Contractor,  on  receiving  written  notice,   shall 
forthwith  dismiss  such  person,  and  s'hall  not  again  employ  him  on 
any  part  of  the  work. 

(27)  When  each  section  of  the  street  has  been  completed,  travel 
is  to  be  allowed  thereon,  if  required  by  the  Engineer;   and  at  the 
time  of  completion  of  the  entire  work,  and  before  the  final  pay- 


PLANS  AND  SPECIFICATIONS.  41 T 

merit,  the  Contractor  will  be  required  to  make  good  at  every  point 
any  defect  which  is  the  result  of  non-compliance  with  any  of  the 
provisions  of  this  contract. 

(.28)  The  said  party  of  the  second  part  hereby  further  agrees 
that  he  will  obey  and  conform  to  all  ordinances  of  the  city  now 
in  force,  or  that  may  be  in  force,  during  the  progress  of  such 
work. 

('29)  If  at  any  time  the  City  Engineer  shall  be  of  the  opinion, 
and  shall  so  certify  in  writing,  that  the  said  work  or  any  part 
thereof  is  unnecessarily  delayed,  or  that  the  said  Contractor  is 
wilfully  violating  any  of  the  conditions  or  covenants  of  this  con- 
tract, or  is  executing  the  same  in  bad  faith,  or  if  the  said  work  be 
not  fully  completed  within  the  time  named  in  this  contract  for 
its  completion,  he  shall  have  the  power  to  notify  the  aforesaid 
Contractor  to  discontinue  all  work,  or  any  part  thereof  under  this 
contract,  by  a  written  notice  to  be  served  upon  the  Contractor, 
either  personally  or  by  leaving  said  notice  at  his  residence  or  with 
his  agent  in  charge  of  the  work,  and  thereupon  the  said  Con- 
tractor shall  discontinue  said  work  or  such  part  thereof.  The  City 
Engineer  shall  thereupon  have  the  power  to  place  such  and  so 
many  persons  as  he  may  deem  advisable,  by  Contract  or  otherwise, 
to  work  at  and  complete  the  work  therein  described,  or  such  part 
thereof,  and  to  use  such  materials  as  he  may  find  on  the  line  of 
said  work,  and  to  procure  other  materials  for  the  completion  of  the 
same,  and  to  charge  the  expense  of  said  labor  and  materials  to  the 
aforesaid  Contractor,  and  the  expense  so  charged  shall  be  deducted 
and  paid  by  the  party  of  the  first  part  out  of  such  moneys  as  may 
be  then  due,  or  may  at  any  time  thereafter  grow  due,  to  the  said 
Contractor  under  and  by  virtue  of  this  agreement,  or  any  part 
thereof;  and  in  case  such  expense  is  less  than  the  amount  which 
would  'have  been  payable  under  this  contract  if  the  same  had  been 
completed  by  said  Contractor,  he  shall  forfeit  all  claim  to  the  dif- 
ference; and  in  case  such  expense  shall  exceed  the  said  sum  he 
shall  pay  the  amount  of  such  excess  to  the  party  of  the  first  part. 

(30)  Guarantee. — Asphalt  pavements  shall  be  kept  in  repair, 
as  specified  herein,  at  the  expense  of  the  Contractor  for  the  term 
of  five  years,  and  all  other  pavements  for  the  term  of  twelve 
months,  from  the  date  of  the  provisional  acceptance  of  the  work, 


418        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

at  which  time  it  is  to  be  turned  over  to  the  city  according  to  the 
provisions  of  Section  34, — provided,  however,  that  should  the  date 
of  final  acceptance  fall  between  December  1st  and  March  31st,  the 
City  Engineer  shall  have  the  right  to  postpone  said  final  acceptance 
until  the  weather  will  permit  an  examination  and  necessary  repairs, 
to  be  made. 

(31)  During  the  performance  of  said  work  the  Contractor  shall 
place  proper  guards  upon  and  around  the  same  for  the  prevention 
of  accidents,  and  at  night  shall  put  up  and  keep  suitable  and 
sufficient  lights,  and  shall  indemnify  and  save  harmless  the  party 
of  the  first  part  against  and  from  all  suits  and  actions,  of  every 
name  and  description,  brought  against  it,  and  all  costs  and  damages 
to  which  it  may  be  put  for  or  on  account  or  by  reason  of  any 
injury  or  alleged  injury  to  the  person  or  property  of  another,  re- 
suiting  from  negligence  or  carelessness  in  the  performance  of  the 
work,  or  in  guarding  the  same,  or  from  any  improper  materials  used 
in  its  prosecution,  or  by  or  on  account  of  any  act  or  omission  of  the 
said  Contractor;   and  the  whole  or  so  much  of  the  moneys  due  the 
said  Contractor,  under  and  by  virtue  of  this  agreement,  as  shall 
or  may  be  considered  necessary  by  the  City  Engineer,  shall  be 
retained  by  the  proper  city  officials  until  all  such  suits  or  claims, 
for  damages  as  aforesaid  shall  have  been  settled,  and  evidence  to 
that  effect  furnished  to  the  satisfaction  of  the  said  Engineer. 

(32)  On  a  street  paved  with  asphalt  if,  at 'any  time  during  the 
period  of  guarantee,  the  work  or  any  part  thereof,  or  any  depres- 
sions, bunches,  or  cracks,  shall,  in  the  opinion  of  the  City  Engineer,, 
require  repairs  or  sanding,  as  provided  for  in  Section  13,  paragraph 
fc,  and  the  Engineer  shall  notify  the  Contractor  to  make  the  re- 
pairs or  do  the  sanding  as  required,  by  a  written  notice  to  be  served 
on  the  Contractor  either  personally  or  by  leaving  said  notice  at 
his  residence  or  with  'his  agent  in  charge  of  the  work,  the  said 
Contractor  shall  immediately  commence  and  complete  the  same 
to  the  satisfaction  of  the  said  Commissioner;  and  in  case  of  failure 
or  neglect  on  his  part  so  to  do  within  forty-eight  hours  from  the 
date  of  the  service  of  the  aforesaid  notice,  then  the  said  Engineer 
shall  have  the  right  to  purchase  such  materials  as  he  shall  deem 
necessary,  and  to  employ  such  person  or  persons  as  he  shall  deem 
proper,  and  to  undertake  and  complete  said  repairs  or  sanding,  and 


PLANS  AND  SPECIFICATIONS.  419 

to  charge  the  expense  thereof  to  the  said  Contractor;  and  the  said 
Contractor  hereby  stipulates  and  agrees  to  pay  all  such  expense 
to  which  the  said  Engineer  may  have  been  put  by  reason  of  the 
neglect  of  the  said  Contractor  to  make  such  repairs  or  to  do  the 
sanding  as  aforesaid. 

(33)  The  Contractor  further  agrees  that  he  will  during  the 
•same  period  lay  and  restore  the  pavement  over  all  openings  made 
by  corporations  or  plumbers  for  making  new  service-connections 
or  repairing,  renewing,  or  removing  the  same,  and  over  all  trenches 
made  for  carrying  sewers,  water-  or  gas-pipes  or  any  other  subsur- 
face pipes  or  conduits,  for  the  building  or  laying  of  which  permits 
may  be  issued  by  the  proper  authorities  for  the  contract  price  per 
square  yard  for  all  openings  whatever,  the  Contractor  or  corpora- 
tion making  such  opening  or  trench  having  taken  such  precautions 
to  prevent  settlement  of  the  filling  over  the  same  as  are  deemed 
necessary  by  the  said  Engineer. 

All  materials  to  be  of  the  same  quality  and  mixed  in  the  same 
manner  as  specified  in  this  contract. 

The  Contractor  further  agrees  not  to  demand  additional  or 
further  payment  on  account  of  repairing  any  injured  or  sunken 
pavement  laid  over  the  repairs  above  described. 

(34)  Just  previous  to  the  expiration  of  the  guarantee  period 
•on  asphalt  pavements  the  entire  work  shall  be  inspected,  and  any 
bunches,  depressions,  or  unevenness  in  the  surface  of  the  pavement 
that  shall  show  a  variation  of  three-eighths  of  an  inch  under  a 
four-foot  straight-edge  or  template,  or  any  crack  wider  than  one- 
fourth  of  an  inch,  or  any  portion  of  the  pavement  having  a  thick- 
ness of  less  than  one  and  one-half  inches  shall  be  immediately  re- 
paired upon  the  order  of  the  City  Engineer,  by  the  heater  process 
or  by  removing  the  entire  pavement  from  the  concrete,  and  re- 
placing it  in  the  same  manner  as  when  originally  laid; — provided, 
that  when  more  than  fifty  per  cent  of  the  surface  of  any  one  block 
requires  repairing  according  to  the  above  conditions,  the  entire 
block  shall  be  taken  up  and  relaid.     Whenever  any  defects  are 
caused  by  the  failure  of  the  concrete  or  the  settlement  of  the  road- 
^vay  from  any  source,  the  entire  pavement,  including  foundation, 
shall  be  taken  up  and  relaid  in  accordance  with  the  specifications. 

Just  previous  to  the  expiration  of  the  guarantee  period  on  stone 


420        STREET  PAVEMENTS  AND  PAVING  M4TERI  LS. 

or  brick  pavements  the  entire  work  shall  be  inspected,  and  any 
defects  caused  by  inferior  material  or  defective  work,  or  settle- 
ments from  any  cause,  shall  be  immediately  repaired  on  the  written 
order  of  the  City  Engineer  and  to  his  satisfaction. 

Should  the  Contractor  for  any  kind  of  pavement  fail  to  make 
the  necessary  repairs  within  six  days  after  being  served  with  the 
above  order,  or  to  perform  the  work  in  a  satisfactory  manner,  the 
City  Engineer  shall  have  the  same  done  and  charge  the  cost  thereof 
to  the  reserve  fund  held  for  that  purpose.  After  all  repairs  have 
been  satisfactorily  made,  the  City  Engineer  will  issue  his  certificate- 
to  that  effect. 

(35)  Payments. — When  the  amount  of  the  contract  is  more 
than  $5000,  on  or  about  the  first  day  of  each  month  a  payment  will 
be  made  to  the  Contractor  of  eighty  per  cent  of  the  value  of  the 
work  performed  during  the  previous  month  upon  the  issuance  of 
the  certificate  of  the  City  Engineer; — provided  that  no  partial  pay- 
ment will  be  made  after  the  expiration  of  the  time  for  the  comple- 
tion of  the  contract. 

When  the  work  has  been  entirely  completed,  and  such  com- 
pletion certified  to  by  the  City  Engineer,  the  entire  amount  due 
under  the  contract  shall  be  paid  to  the  Contractor  less  any  pay- 
ments previously  made  and  any  amounts  rightly  retained  under  the 
provisions  of  these  specifications. 

On  all  work  guaranteed  for  five  years  ten  per  cent  of  the  amount 
of  the  contract  price  shall  be  retained  till  the  end  of  the  guarantee- 
period;  but  the  contractor  will  be  allowed  to  deposit  city  bonds 
with  the  financial  agent  of  the  city  to  the  amount  of  the  reserve- 
due,  when  the  entire  balance  will  be  paid.  During  the  guarantee 
period  he  will  be  allowed  to  draw  all  interest  due  upon  the  bonds,, 
and  upon  the  final  acceptance  of  the  work,  and  the  Engineer's 
certificate  to  that  effect,  the  entire  amount  will  be  returned  to  the 
Contractor,  less  any  amount  paid  out  for  repairs. 

On  work  guaranteed  for  twelve  months  a  sum  of  ten  cents  per 
square  yard  for  granite  on  sand,  and  fifteen  cents  for  stone  or  brick 
pavements  on  concrete,  shall  be  retained  until  the  final  acceptance, 
when  the  said  retained  sum,  less  any  amount  expended  for  neces- 
pary  repairs,  will  be  paid. 


CHAPTER  XIII. 

THE  CONSTRUCTION  OF  STREET-CAR  TRACKS  IN  PAVED  STREE1S  AND 

ROADWAYS. 

THE  problem  of  how  to  construct  street-car  tracks  in  the  best 
manner  in  paved  streets  has  been  troubling  engineers  in  charge 
of  pavement  construction  for  many  years.  In  the  early  days  of 
street-railways,  when  the  streets  were  paved  with  cobblestones  and 
when  street-cars  were  small  and  drawn  by  horses  at  a  speed  of  five 
or  six  miles  an  hour,  this  question  was  not  so  important.  But 
in  the  present  time  of  asphalt  and  other  improved  pavements,  of 
rubber  tires,  bicycles  and  automobiles,  and  with  cars  weighing 
from  10J  to  12  tons  propelled  by  electricity  along  our  streets  at  a 
speed  of  from  eight  to  fifteen  miles  per  hour,  the  importance  of 
good  and  smooth  track-construction,  both  to  the  general  public 
and  to  the  street-car  company,  can  hardly  be  overestimated. 

There  is  no  doubt  that  the  street-car  track  is  detrimental  to. 
any  pavement,  but  it  is  a  necessary  evil,  for  it  is  well  recognized  at 
the  present  time  that  no  one  thing  tends  to  develop  and  build  up 
a  city  as  does  a  good  system  of  street-cars. 

The  problem  of  the  construction  of  street-car  tracks  is  very 
different  from  that  of  the  ordinary  steam-railways.  The  steam- 
cars  run  on  their  own  right  of  way,  making  stops  only  at  long 
intervals,  and  the  tracks  can  be  constructed  in  such  a  manner  as. 
will  give  the  best  results  as  regards  economy  of  construction  and 
maintenance,  with  no  regard  for  the  wishes  of  others,  except  at 
street  or  road  crossings. 

Street-cars,  however,  run  through  public  highways  which  are 
being  used  constantly  by  vehicles,  and  crossed  often  by  pedestrians, 
and  their  construction  must  be  such  as  will  not  only  accommodates 

421 


422        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

their  own  cars,  but  also  interfere  as  little  as  possible  with  the 
ordinary  vehicular  traffic  of  the  street. 

It  must  be  remembered,  however,  in  this  connection  that  there 
are  two  travelling  publics,  the  one  in  the  cars  and  the  other  using 
private  vehicles,  and  while  the  former  uses  the  vehicles  of  the 
corporations,  operated  in  a  public  thoroughfare,  any  action  which 
tends  to  discommode  or  interfere  unnecessarily  with  the  action 
of  the  cars  must  discommode  to  a  great  extent  a  very  large  pro- 
portion of  the  travelling  public.  Probably  40  per  cent  of  all  the 
business  men  in  the  average  American  city  of  more  than  100,000 
inhabitants  depend  more  or  less  upon  the  street-cars  for  their 
convenience  every  day. 

The  authorities  of  street-railways,  and  the  cities  in  which  they 
are  operated,  generally  differ  considerably  in  their  ideas  of  what  is 
the  proper  construction  for  the  tracks.  The  street-car  companies 
are  interested  only  to  perform  their  work  economically.  A  con- 
struction that  will  allow  their  rolling-stock  to  be  operated  with  the 
least  amount  of  wear  and  tear  and  will  cost  the  least  for  original 
•construction,  as  well  as  maintenance,  is  what  they  desire.  On  the 
other  hand,  the  city  authorities  are  not  interested  to  any  great 
•extent,  either  in  the  cost  of  construction  or  maintenance.  They 
wish  a  construction  that  can  be  carried  out  with  little  obstruction 
to  the  general  travel  of  the  street,  will  require  but  little  interfer- 
ence with  the  pavement  for  maintenance  and  repairs,  and  present 
little  obstruction  to  the  general  traffic. 

In  early  track-construction  the  railway  companies  sometimes 
sought  to  lay  a  rail  that  would  be  very  obstructive  to  travel.  When 
a  track  is  such  that  vehicles  seek  it  in  preference  to  the  street, 
the  operation  of  the  street-cars  is  interfered  with,  and  the  com- 
panies seek  every  means  to  prevent  this. 

With  the -rough  stone  pavements  of  twenty-five  years  ago,  the 
special  form  of  the  rail  added  very  little  to  the  general  roughness 
of  the  street,  but  railway  companies  must  recognize  at  the  present 
time  that  smooth  and  improved  pavements  have  come  to  stay,  and 
that  they  must  adopt  a  method  of  track  construction  that  will  con- 
form to  these  pavements. 

The  ideal  construction  seems  to  be  one  in  which  the  track  is 
a  part  of  the  pavement  itself,  and  not  a  separate  and  definite  part 


THE  CONSTRUCTION  OF  STREET- CAR   TRACKS.        423 

of  the  work,  and  the  track  and  pavement  should  be  studied  to- 
gether as  one  whole.  The  time  of  probable  renewal  of  each  part 
should  be  taken  into  consideration,  and  the  design  of  each  made  so 
as  best  to  accommodate  these  renewals.  This,  however,  is  not  verv 
often  practicable,  from  the  fact  that  it  very  seldom  happens  that 
&  pavement  and  a  railway-track  are  constructed  at  the  same  time, 
so  that  certain  modifications  or  concessions  can  be  agreed  upon 
and  the  best  results  for  both  obtained. 

The  question  should  be  taken  up  by  the  railway  and  city 
authorities  conjointly,  as  if  both  were  owned  and  were  to  be  oper- 
ated by  one  interest;  and  after  the  details  which  would  be  best 
under  this  arrangement  were  determined  upon,  general  modifica- 
tions could  be  made  if  desired,  so  that  the  interest  of  either  party 
would  not  suffer. 

Street-railway  companies,  having  operated  in  public  highways 
for  so  long  a  time,  with  an  inexpensive  construction  determined 
upon  by  themselves,  find  it  very  hard  at  times  to  meet  the  require- 
ments of  modern  pavements  and  the  present  city  officials,  but 
they  soon  find  that  it  is  better  economy  as  well  as  better  policy  to 
adopt  a  construction  that  will  be  both  durable  and  satisfactory  to 
the  municipal  authorities. 

The  question  as  to  the  proper  remuneration  to  be  made  to 
municipalities  for  the  use  of  its  highways  for  the  operation  of 
street-cars  has  never  been  definitely  settled.  In  some  cities  it  is 
arrived  at  by  the  company's  paying  a  certain  amount  to  the  city, 
sometimes  based  upon  its  receipts,  the  number  of  passengers 
carried,  or  sometimes  a  lump  sum^  determined  upon  in  advance. 

In  some  cities,  also,  the  cost  of  paving  is  settled  in  much  the 
same  way;  but,  as  a  rule,  the  actual  amount  of  the  street  to  be 
cared  for  by  the  railway  company  is  defined  either  in  its  charter  or 
by  special  legislation.  No  attempt  will  be  made  in  tkis  connection 
to  treat  the  question  of  value  from  the  franchise  standpoint,  but 
simply  with  reference  to  the  care  of  the  pavement. 

In  1854  an  Act  was  passed  by  the  Massachusetts  Legislature 
incorporating  the  Dorchester  Avenue  Railway  Co.  and  requiring  it 
to  keep  in  repair  the  whole  of  the  bed  of  any  road  in  the  town  of 
Dorchester  in  which  it  might  lay  tracks.  In  the  following  year, 
however,  this  Act  was  amended  by  a  repeal  of  this  clause  and  the 


424        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

( 

substitution  of  a  provision  requiring  only  that  part  of  the  road 
occupied  by  the  tracks  to  be  kept  in  repair,,  and  denning  that 
portion  "  to  be  the  space  between  the  rails  and  so  much  on  each 
side  thereof  as  shall  be  within  a  perpendicular  let  fall  from  the 
extreme  width  of  any  car  or  carriage  used  thereon,  being  the  space 
from  which  public  travel  is  excluded  during  the  passing  of  said 
car  or  carriage." 

In  Baltimore,  Md.,  the  street-car  companies  pave  and  keep  in 
repair  the  space  between  their  tracks,  and  2  feet  on  each  side. 

In  Buffalo,  N.  Y.,  different  conditions  exist  in  regard  to  the 
paving  requirements  by  the  different  companies,  but  in  general  the 
maintenance  of  the  street  between  the  tracks  and  2  feet  outside 
is  required. 

Although  in  some  locations  no  paving  at  all  is  required  from 
the  street-car  companies,  in  New  York  a  bill  was  passed  in-  1895 
which  provided  that  one-fourth  of  the  cost  of  repaying  any  street  in 
Brooklyn  in  which  was  operated  a  street-railway  should  be  assessed 
against  the  company  owning  such  track.  A  great  many  streets  were 
paved  under  this  law,  but  at  the  present  time  no  tax  has  been  col- 
lected from  the  street-car  companies.  This  question,  however,  will 
probably  be  settled  by  a  general  New  York  statute  which  will  be 
referred  to  later  on. 

In  Chicago,  111.,  the  conditions  under  which  the  companies 
now  operate  require  that  they  pave  and  maintain  16  feet  in  width 
of  the  street  in  case  of  double  tracks  and  8  feet  in  the  case  of 
single  tracks,  with  a  pavement  of  as  good  quality  as  that  of  the  rest 
of  the  street. 

In  Detroit,  Mich.,  the  railway  company  pays  no  special  tax  on 
the  gross  earnings,  is  required  to  do  no  paving  either  between  its 
tracks  or  other  part  of  the  street  in  which  they  are  located, 
is  not  required  to  make  pavement  repairs  if  the  streets  -are  dis- 
turbed for  railroad  repair  work,  and  the  concrete  base  on  which  its 
tracks  are  laid  is  put  down  by  the  city. 

In  Indianapolis,  Ind.,  a  readjustment  of  the  terms  of  the  orig-  t 
inal  franchise  was  made  in  1878,  when  a  provision  requiring  the 
road  to  repave  between  its  tracks  was  changed  so  as  to  read  "  repair 
between  its  tracks."    On  account  of  this  action  there  is  considerable 
feeling  between  the  taxpayers  and  the  railway  company. 


THE  CONSTRUCTION  OF  STREET- CAR   TRACKS.        425 

In  Xew  York  City  it  is  held  that  the  different  companies  are 
bound  by  Chapter  676  in  Laws  of  1892,  a  portion  of  which  reads 
as  follows: 

"  Every  street-railroad,  so  long  as»  it  shall  continue  to  use 
any  of  its  tracks  in  any  street,  avenue,  or  public  place  in  any 
city  or  village,  shall  pave  and  keep  in  permanent  repair  that 
portion  of  such  street,  avenue,  or  public  place  between  its  tracks 
or  rails  of  its  tracks,  and  two  feet  in  width  outside  of  its 
tracks,  under  the  supervision  of  the  proper  local,  authorities,  and 
whenever  required  by  them  to  do  so,  and  in  such  manner  as  they 
may  prescribe.  In  the  case  of  neglect  of  any  corporation  to  make 
these  pavements  or  repairs  after  the  expiration  of  thirty  days' 
notice  to  do  so,  the  local  authorities  may  make  same  at  the  expense 
of  such  corporation." 

The  street-car  companies,  however,  have  not  always  lived  up 
to  this  requirement,  and  it  was  stated  in  a  paper  read  before  the 
American  Society  of  Civil  Engineers  in  December,  1896,  that  bills 
aggregating  more  than  $700,000  had  accumulated  against  surface 
railways  on  Manhattan  Island  from  1889  to  1895  inclusive. 

The  street-car  companies  in  the  city  of  Philadelphia  have  prob- 
ably expended  more 'money  for  pavements  in  city  streets  than  any 
other  city  in  the  world.  In  1892  the  streetrrailways  changed  their 
power  from  horses  to  electricity,  and  an  agreement  was  entered 
into  between  the  companies  and  the  city  authorities  by  which  the 
roads  agreed  to  pave  and  maintain  the  streets  through  wTiich  they 
operated,  from  curb  to  curb.  The  streets  of  Philadelphia  being 
so  narrow  that  in  most  cases  only  one  track  is  operated  for  each 
street,  a  large  amount  of  street  mileage  is  occupied  by  the  street- 
car companies.  It  is  said  that  on  January  1,  1898,  there  had  been 
expended  by  the  different  companies  for  street  pavement  since 
1892,  w<hen  the  above  agreement  was  entered  into,  a  sum  amount- 
ing to  about  $12,000,000. 

In  Rochester,  N.  Y.,  the  railway  company  accepted  the  pro- 
visions of  the  statute  previously  referred  to  as  far  as  repairs  to  the 
pavement  were  concerned,  but  it  did  not  admit  its  obligation  in 
regard  to  new  pavements.  In  a  test  case  brought  to  settle  this 
point,  the  .two  following  questions  were  asked: 

"  Are  the  abutting  owners  on  Lyell  Avenue  liable  for  the  cost 


426        STREET  PAVEMENTS  AND  PAVING  MATEMIALS. 

of  constructing  a  new  pavement  between  the  tracks,  the  rails 
of  the  tracks,  and  2  feet  in  width  outside  of  the  tracks  of  the 
Rochester  Eailway  Co.?  Second:  Is  the  duty  of  the  Common 
Council  of  the  city  of  Rochester  to  request  the  railway  company  to 
construct  a  pavement  between  its  tracks,  the  rails  of  its  tracks,  and 
for  2  feet  outside  thereof,  on  Lyell  Avenue,  before  the  city  con- 
tstructs  such  pavement,  mandatory  ?  " 

The  court  decided  the  first  question  in  the  negative,  and  the 
second  in  the  affirmative.  The  railway  company  not  being  a  party 
to  the  suit,  the  decision  was  not  accepted  by  them  as  final,  and 
the  case  is  being  carried  through  the  courts  at  the  present  time 
in  a  different  form.  The  city  authorities,  however,  have  carried 
out  the  work  of  paving  the  streets  occupied  by  the  railway  com- 
pany, and  have  made  out  the  bills  as  if  the  law  were  in  force. 

In  St.  Louis,  Mo.,  the  companies  are  required  to  pave  within 
the  tracks  and  12  inches  outside  of  the  rails,  with  a  material  ap- 
proved by  the  Commissioner  of  Public  Works. 

In  Toronto,  Can.,  the  street-car  tracks  are  owned  by  the  city, 
and  in  1891  the  exclusive  privilege  of  operating  them  was  granted 
to  the  Toronto  Railway  Co.  In  the  agreement  made  between  the 
city  and  the  company  it  is  required  that  the  purchaser  shall  main- 
tain the  ties,  stringers,  rails,  turnouts,  curves,  etc.,  in  a  state  of 
thorough  efficiency  and  to  the  satisfaction  of  the  City  Engineer, 
and  shall  remove,  renew,  or  replace  same  as  circumstances  may 
require  and  as  the  City  Engineer  may  direct.  When  a  street  upon 
which  the  tracks  are  now  laid  is  to  be  paved  in  a  permanent  man- 
ner on  concrete  or  other  foundation,  then  the  purchaser  shall  re- 
move the  present  tracks  and  superstructure,  and  repave  the  same 
according  to  the  best  modern  practice,  by  improved  rails,  points, 
and  substructure  of  such  description  as  may  be  determined  upon 
by  the  City  Engineer  as  most  suitable  for  the  purpose.  In  the 
event  of  the  purchaser  desiring  to  make  any  repairs  or  alterations 
to  the  ties,  stringers,  rails,  turnouts,  curves,  etc.,  on  paved  streets, 
the  purchaser  shall  repave  the  portion  of  the  railway  so  torn  up  at 
his  own  expense. 

When  the  purchaser  desires,  or  is  required,  to  change  any  ex- 
isting tracks  or  substructure  for  the  purpose  of  operating  by  elec- 
tricity or  other  motive  power  approved  by  the  City  Engineer  and 


THE  CONSTRUCTION  OF  STREET-CAR   TRACKS.        427 

confirmed  by  the  Council,  the  city  will  lay  down  permanent  pave- 
ment in  conjunction  therewith  upon  the  track  allowance  as  herein 
defined  to  be  occupied  by  said  new  tracks  and  substructures.  This 
at  first  applied  only  to  existing  main  lines  and  thereafter  to  branch 
lines  or  extensions  to  main  lines  and  branches.  Under  the  terms 
of  the  agreement  the  company  pays  the  City  Treasurer  $1600  per 
annum  per  mile  of  double  track  and  eight  per  cent  of  the  gross 
receipts,  and  when  the  receipts  exceed  $1,000,000  ten  per  cent  is  to 
be  paid. 

In  the  city  of  Washington,  D.  C.,  the  amount  of  pavement  to 
be  cared  for  by  street-railway  companies  is  proyided  for  by  an  Act 
of  Congress  approved  June  11,  1878.  This  requires  that— 

"  When  any  street  or  avenue  through  which  a  street-railway 
runs  shall  be  paved,  such  railway  company  shall  bear  all  of  the 
expense  for  that  portion  of  the  work  lying  between  the  exterior 
rails  of  the  tracks  of  such  roads  and  for  a  distance  of  2  feet  from 
the  exterior  to  such  track  or  tracks  on  each  side  thereof  and  of 
keeping  same  in  repair,  but  the  said  railway  company,  having 
conformed  to  the  grades  established  by  the  Commissioners,  may 
use  such  cobblestones  or  Belgian  blocks  for  paving  their  tracks  or 
the  spaces  between  their  tracks  as  the  Commissioners  may  direct." 

Much  the  same  conditions  and  requirements  exist  in  European 
as  in  American  cities  in  regard  to  the  pavement  between  the  tracks, 
although  the  street-car  mileage  is  much  less  than  in  American  cities 
of  the  same  population. 

The  construction  of  railways  in  Great  Britain  is  governed  by 
the  Tramways  Act  of  1870.  As  regards  pavements,  it  provides  that 
the  companies  shall  repair  and  maintain  the  space  between  the 
tracks  and  18  inches  on  each  side.  If  not  properly  done  it  may, 
after  seven  days'  notice,  be  done  by  the  road  authorities  and 
charged  to  the  company. 

In  Amsterdam,  Holland,  the  street-car  company  is  obliged  to 
put  the  streets  in  good  order  after  construction  and  to  maintain 
them  between  the  rails  and  20  inches  on  each  side,  and  where  the 
street  is  not  paved  this  same  space  is  required  to  be  paved  by  the 
company.  In  addition  to  this  the  street-car  company  pays  the  city 
the  sum  of  $600,000  for  general  widening  of  streets,  construction 
and  paving  of  new  roads,  the  building  of  new  and  changing  and 


428        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

widening  of  old  bridges,  the  filling  and  earthing  over  canals  and 
laying  sewer-pipes. 

The  city  of  Berlin,  Germany,  has  a  very  elaborate  and  specific 
contract  with  the  street-railway  companies.  The  requirements  for 
laying  and  maintaining  pavements  are  entered  into  in  great  detail, 
but  in  the  main  compel  the  companies  to  lay  a  permanent  pave- 
ment, whenever  the  remainder  of  the  street  is  so  paved,  on  the 
space  occupied  by  the  tracks  and  to  a  distance  of  12  inches  on  both 
sides  of  each  rail.  They  are  also  required  to  keep  the  pavement 
between  their  rails  and  26  inches  outside  of  the  outer  rails  in  good 
condition. 

In  Hamburg,  Germany,  a  contract  between  the  city  and  one 
of  the  largest  of  the  railway  companies  requires  the  company  for 
a  period  of  twenty-five  years  from  1898  to  pay  the  city  in  lieu  of 
any  paving  or  street-cleaning  a  charge  of  1  pfennig  (|  cent)  per 
passenger  carried  for  a  cash  fare  and  five  per  cent  on  commutation- 
tickets. 

In  Vienna,  Austria,  the  street -car  company  is  obliged  to  pave 
and  maintain  a  space  of  8J  feet  in  width  for  each  track. 

The  above  gives  a  general  idea  of  the  requirements  in  a  num- 
ber of  cities  in  this  country  and  in  Europe  as  regards  the  cost  of 
keeping  the  portion  of  the  streets  occupied  by  street-car  tracks 
well  paved. 

Location. 

The  location  of  the  street-car  tracks  is  important  and  should 
be  and  is  generally  under  the  direction  of  the  city  authorities.  As 
a  rule,  it  is  better  that  they  be  located  in  the  centre  of  the  street, 
but  in  case  any  large  tract  of  land  adjacent  to  a  street  is  occupied 
by  parks,  cemeteries,  or  other  public  grounds,  it  is  often  more  con- 
venient for  the  general  public  that  the  tracks  be  located  on  one  side. 
This  gives  some  space  for  general  traffic  and  generally  will  accom- 
modate that  portion  of  the  public  using  street-cars  better,  as,  in  the 
case  of  both  cemeteries  and  parks,  the  majority  of  the  passengers 
on  that  portion  of  the  line  will  be  on  the  side  where  the  track  is 
located  and  so  be  able  to  take  the  car  without  entering  the  street. 

In  country  roads  outside  of  villages  it  will  be  more  satisfactory 


THE  CONSTRUCTION  OF  STREET-CAR   TRACKS.        429 

to  have  the  location  on  one  side,  as  that  will  leave  the  centre  of 
the  road  free  for  general  travel.  In  such  case  the  space  between 
the  tracks,  in  many  instances,  need  not  be  paved,  and  where  the 
roadway  is  not  improved  to  any  great  width  the  track  can  often  be 
laid  outside  of  the  improvement.  In  speaking  on  this  point,  in  a 
paper  before  the  American  Society  of  Civil  Engineers,  read  in  De- 
cember, 1896,  Mr.  James  Owen  says: 

"  On  a  50-foot  roadway  a  20-foot  driveway  in  the  centre,  the 
track  on  each  side  and  within  9  feet  of  access  to  houses,  gives  good 
satisfaction,  preserves  the  driveway,  and  lessens  repairs. 

"  In  a  60-foot  roadway  and  14-foot  driveway  outside  the  tracks, 
all  the  requirements  are  attained.  In  a  roadway  of  less  than  50 
feet  the  tracks  must  of  necessity  be  in  the  centre.  Where  only  one 
track  is  laid  on  a  country  road  the  track  should  be  on  one  side  with 
the  switches  toward  the  centre. 

"  Whenever  a  track  is  laid  in  the  centre  of  a  country  road  it 
should  always  be  paved  with  some  material  whether  the  road  as 
well  is  improved  or  not/7 

In  Beacon  Street,  Boston,  the  roadway  is  extremely  wide,  and 
parks  are  located  in  the  centre,  sodded  with  grass,  and  in  many 
places  set  out  with  trees  and  ornamental  shrubs.  In  many  other 
streets  in  and  near  Boston  the  tracks  are  located  on  a  strip  given 
up  wholly  to  them. 

Canal  Street,  New  Orleans,  is  170  feet  6  inches  wide,  and  the 
sidewalks  are  18  feet  in  width.  In  the  centre  of  the  street  is  a 
space  60  feet  wide,  called  "  neutral  strip,"  in  which  four  lines  of 
street-car  tracks  are  laid.  On  each  side  of  the  "  neutral  strip  " 
are  carriage  driveways  37  feet  3  inches  wide.  This  street  is  paved 
with  asphalt,  the  entire  cost  being  borne  by  the  city,  including  the 
"  neutral  strip,"  which  is  wholly  occupied  by  railway  companies. 

The  first  charter  for  a  street-railway  company  in  Massachu- 
setts was  granted  by  the  Legislature  to  the  Metropolitan  Railway 
Company  of  Boston  in  1853,  and  about  the  same  time  the  first 
street-railway  track  was  laid  on  Fourth  Avenue  in  New  York 
City.  A  "  rail-bus  "  was  built  and  operated  for  a  short  time  in  the 
latter  city  by  John  Stephenson  in  1832.  The  first  horse-railroad 
was  operated  in  January,  1858. 

In  Paris  the  first  tramway  was  constructed  in  1853,  although 


430        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


not  very  much  developed  during  the  first  twenty  years;  while  the 
first  street-car  lines  in  London  and  in  Glasgow  were  constructed 
by  Americans  in  1860.  These  early  companies  were  very  crude  in 
their  operation  and  construction  as  compared  with  the  present 
time.  The  first  rail  was  practically  a  piece  of  flat  iron  spiked  to 
a  stringer  with  a  groove  in  which  the  flange  of  the  wheel  ran;  but 
as  traffic  increased  a  more  substantial  rail  was  required,  and  that 
shown  in  Fig.  19  was  adopted.  This  was  spiked  to  the  stringer^ 

T~ 


FIG.  19. 

which  itself  rested  on  ties.  The  spikes  and  rails  would  soon  be- 
come loosened  and  the  joints  rough  and  uneven,  but  with  the 
light  cars  of  the  time  they  could  be  used,  although  to  the  great 
discomfort  of  the  passengers. 

Fig.  20  represents  a  car-rail  of  the  same  type  used  on  curves.. 


FIG.  20. 

The  sharp  edge  of  Fig.  19  made  it  very  difficult  for  teams  to  cross- 
the  tracks,  and  consequently  the  type  shown  in  Fig.  21  was 
adopted.  This  allows  heavily  loaded  teams  to  cross  the  tracks 
more  rapidly,  but  gives  no  better  service  to  either  cars  or  passen- 
gers. 

Fig.  22  shows  a  further  development  with  a  groove  for  the 
flange  of  the  wheel,  but  without  the  modification  of  Fig.  21,  allow- 
ing the  passage  of  wagons  over  the  tracks. 

Fig.  23  shows  what  was  generally  known  as  the  centre-bearing- 


THE  CONSTRUCTION  OF  STREET-CAR   TRACKS.        431 

rail.  This  is  practically  Fig.  22  doubled.  It  has  been  claimed  by 
many,  if  not  admitted  by  the  companies  themselves,  that  the  main 
object  of  this  rail  was  to  make  the  track  as  obnoxious  as  possible 
to  vehicular  traffic,  and  any  one  who  has  seen  this  construction 
in  a  paved  street  can  see  that  it  has  pretty  successfully  accom- 


FIG.  21. 


FIG.  22. 


plished  its  purpose.  When  it  is  laid  in  duplicate,  with  two  rails 
on  one  stringer  as  it  existed  in  Fourteenth  Street,  New  York  City, 
in  the  spring  of  1900,  it  would  seem  as  if  it  had  fulfilled  its  pur- 
pose beyond  the  utmost  expectations  of  the  street-car  companies 
themselves.  It  was  expected  that  when  one  side  of  the  rail  was 


432        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

worn  out  it  could  be  turned  end  for  end  and  used  on  the  other 
side. 

About  this  time  an  attempt  was  made  to  construct  a  rail  with 
a  renewable  head,  it  being  recognized  that  while  the  head  of  the 
rail  might  be  worn  out,  the  lower  part  and  base  would  be  as  good 
as  ever.  In  order  to  accomplish  this  the  rails  were  made  in  two 
parts,  so  that  when  it  was  worn  it  could  be  taken  out  and  renewed 
without  disturbing  the  ties  or  the  base  of  the  rail  even.  Fig.  24 
shows  a  type  of  this  rail. 


FIG.  24. 

Fig.  25  shows  a  rail  built  somewhat  on  this  plan,  but  differing 
in  detail,  the  rail  itself  being  supported  on  iron  chairs  which  were 
spiked  to  the  ties.  Quite  a  large  quantity  of  these  rails  was  used 
in  Brooklyn,  N.  Y. 

When  it  became  necessary  in  the  development  of  street-rail- 
ways to  change  the  power  from  horses  to  electricity,  it  was  soon 
discovered  that  it  would  be  impossible  to  operate  the  cars  on  much 
of  the  construction  that  has  been  described.  Consequently  new 
forms  of  rail  were  attempted,  and  steel  was  used  in  their  con- 
struction. Fig.  26  shows  the  girder  rail  that  was  designed  prac- 
tically on  the  lines  of  Fig.  23,  with  all  of  its  objectionable 
features. 


THE  CONSTRUCTION  OF  STREET-CAR  TRACKS.        433 


FIG.  25. 


FIG.  26. 


4:34        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Fig.  27  shows  what  is  known  as  the  side-bearing  rail.  This 
form,  with  slight  modifications,,  has  been  used  perhaps  more  in 
American  cities  than  any  other  type.  It  makes  a  good  roadway 
for  vehicles,  but  it  is  difficult  for  a  loaded  team  to  turn  out  from 
the  track.  On  account  also  of  its  wide  tram  it  is  very  difficult  to 
pave  up  to  it  with  any  kind  of  block  pavement,  as  any  little  set- 
tlement at  the  end  of  a  block  will  bring  the  block  below  the  tram 
of  the  rail,  when  abnormal  wear  will  arise  and  a  rut  soon  form. 


FIG.  27. 

Fig.  28  shows  a  grooved  rail  that  has  been  used  to  a  great  ex- 
tent in  New  York  City  and  is  known  as  the  Trilby  rail.  The  lip 
of  this  rail  is  extended  to  a  considerable  distance  beyond  the 
groove,  allowing  the  wheel  of  any  vehicle  whose  wheel-base  is 
slightly  less  than  the  gauge  of  the  track  to  run  on  the  iron  lip 
rather  than  inside,  as  it  otherwise  would,  with  the  liability  of 
forming  a  rut.  This  has  the  same  objection  as  regards  paving 
as  Fig.  27,  and  the  lip  of  the  rail  is  also  kept  a  short  distance 
below  the  head.  This  is  objectionable,  because  it  provides 
a  guide  to  a  certain  extent  for  wheels  and  serves  to  keep 
the  horses  travelling  on  the  track,  as  they  easily  learn  the  line  of 
least  resistance  and  are  guided  by  very  slight  changes.  The  typical 
rail  should  be  one  that  would  neither  invite  nor  repel  traffic,  and 


THE  CONSTRUCTION  OF  STREET- CAR   TRACKS.        435 

of  such  shape  that  horses  could  not  tell  whether  the  wheels  were 
or  were  not  following  the  track. 


FIG.  28. 


_t 


FIG.  29. 


Fig.  29  shows  a  modification  of  this  rail,  designed  by  the  Chief 
Engineer  of  the  Brooklyn  Heights  Railway  Co.,  which  avoids  the 
objections  spoken  of. 


436        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

The  street-car  companies  object  to  the  grooved  rail  on  account 
of  the  difficulty  with  which  the  groove  is  kept  clean.  This  is  par- 
ticularly important  with  electric  traction.  This  last  rail  was  de- 
signed especially  with  the  groove  formed  in  such  a  way  that  it 
would  be  kept  clean  by  the  action  of  the  wheel-flange. 

Fig.  30  shows  a  section  of  a  grooved  rail  used  by  the  West  End 
Street-Car  Co.  of  Boston.  This  has  a  lip  with  a  groove  quite  a  dis- 
tance below  the  slot  of  the  rail  and  would  be  a  decided  guide  to 
wheels. 

T" 


FIG.  30. 

Fig.  31  shows  a  section  of  a  rail  used  in  the  Boston  subway. 
This,  it  will  be  seen,  is  a  simple  tee  rail  with  a  flange  bolted  on, 
forming  a  groove.  This,  being  used  in  the  subway  is  of  course  not 
objectionable. 

It  is  generally  conceded  that  the  tee  rail  as  used  on  steam-rail- 
roads is  the  most  economical  rail  for  any  track,  and  the  modifica- 
tions here  shown  are  made  on  account  of  the  pavement  and  other 
requirements  peculiar  to  street-railways,  but  on  country  roads 
where  traffic  is  comparatively  light,  and  the  rails  form  no  great 
obstruction  on  account  of  location,  etc.,  the  rail  as  shown  in  Fig. 
32  can  be  used  to  good  advantage  to  the  railway  company  and  no 
detriment  to  the  public. 

The  street-car  companies  recognize  the  necessity  of  a  permanent 


THE  CONSTRUCTION  OF  STREET-CAR  TRACKS.        437 


FIG.  31. 


FIG.  32. 


438        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

construction  in  the  improved  pavements,  and  for  the  last  four  or 
five  years  have  been  experimenting  with  a  view  to  obtaining  the 
best  and  most  economical  method  of  construction. 

Fig.  33  shows  a  section  of  a  track  as  laid  on  a  street  paved  with 
asphalt  in  Buffalo  by  the  Buffalo  Railway  Co.  It  will  be  noticed 
that  both  ties  and  rails  rest  on  concrete,  giving  a  construction 
that  is  absolutely  rigid,  except  what  resilience  is  gained  from  the 
elasticity  of  the  ties.  In  speaking  of  this  plan,  a  representative 
of  the  company  says  that  they  have  used  concrete  construction  in 
Buffalo  since  1897.  The  rails  themselves  rest  directly  on  concrete 
beams  and  are  held  to  gauge  by  tie-rods.  In  this  construction  the 
concrete  beam  was  formed  and  allowed  to  set,  and  then  the  rails 
were  placed  upon  the  beams  with  steel  ties,  and,  after  being  sur- 


GROUT 


FIG.  33. 

faced  with  wedges,  the  space  between  the  concrete  beam  and  the 
rail  was  filled  with  grouting. 

In  1899,  however,  the  construction  was  changed  to  that  as 
shown  in  the  figure.  The  rails  were  9  inches  deep  and  60  feet  long. 
They  were  drilled  for  tie-rods  every  10  feet  and  with  one  hole  only 
at  each  end,  the  rail  being  temporarily  fastened  with  spliced  bars. 
Oak  ties  5  inches  by  7  inches  by  7  feet  were  used,  spaced  5  feet  from 
centre  to  centre,  every  other  tie  being  tamped  with  crushed  stone 
and  the  surfacing  and  lining  being  done  by  means  of  these  ties. 
The  alternate  ties  were  then  tamped  with  concrete  their  entire 
length,  and  a  beam  of  concrete  about  8  inches  deep  and  15  inches 
wide  was  laid  under  the  rail.  The  use  of  the  stone-tamped  ties  was 
for  the  purpose  of  expediting  the  work,  as  the  track  could  be  spiked, 
gauged,  lined,  and  surfaced  by  means  of  them  quicker  than  if  the 
concrete  beam  was  first  made. 


THE  CONSTRUCTION  OF  STREET-CAR   TRACKS.        439 

In  places  where  common  paving  was  used  the  amount  of  con- 
crete included  in  the  above  statement  was  all  that  was  required,  but 
where  block  paving  was  laid  the  space  between  the  ties  and  for  a 
distance  of  2  feet  outside  of  the  rail  was  filled  with  a  6-inch  layer  of 
concrete  as  a  foundation  for  the  paving.  All  concrete  was  laid  of  the 
best  grade  of  Portland  cement  in  the  proportion  of  one  part  of 
cement,  three  of  sand,  and  five  of  broken  stone. 

During  the  process  of  spiking,  lining,  etc.,  the  rails  were  joined 
temporarily  with  space-bars,  two  bolts  only  being  used  to  a  joint. 
After  the  concrete  had  set  for  72  hours  the  bolts  were  removed 
and  the  joints  electrically  welded.  For  this  purpose  an  ordinary 
Bessemer  bar,  3  inches  wide,  1  inch  thick,  and  15  inches  long  was 
used,  one  on  each  side  of  the  web  of  the  rail,  and  three  welds  were 
made  on  a  joint,  one  at  each  end  of  the  bar  and  one  at  the  point 
where  the  rails  abutted.  The  company  did  not  deem  it  necessary 
to  introduce  expansion-joints  to  take  care  of  expansion  and  contrac- 
tion, and  in  the  spring  of  1900  still' thought  that  they  were  right. 

The  company  states  that  under  the  old  method  they  could  lay 
about  500  feet  of  track  per  day,  but  with  that  just  described  they 
were  able  to  lay  2500  feet  in  the  same  time.  The  officials  say  all 
iheir  track  on  concrete  beam  is  in  first-class  shape,  making  very 
smooth  riding,  with  little  or  no  inequalities  in  the  surface. 

Fig.  34  shows  the  construction  in  a  common  stone  pavement. 


FIG.  84. 

It  differs  from  the  above  in  having  the  concrete  only  under  the 
ties  and  in  the  beam  under  the  rails.  It  will  be  noticed  in  Fig.  33 
as  well  as  Fig.  34  that,  although  the  street  itself  is  paved  with 
asphalt,  the  space  between  the  rails  and  tracks  is  paved  with  stone. 
It  is  without  doubt  more  economical  for  the  railway  company. 
Fig.  35  shows  the  standard  tie-construction  of  the  Borough  of 


440        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Brooklyn,  New  York  City,  as  established  by  the  Department  of 
Highways  for  streets  paved  with  stone  on  a  concrete  base.  This- 
requires  6  inches  of  concrete  under  the  ties,  and  would  make  a 
thickness  between  the  ties  of  12  inches. 

Fig.  36  shows  the  construction  recommended  with  a  concrete 
beam  under  the  same  conditions  as  above.  A  portion  of  track  was 
constructed  in  this  manner  in  1899.  No  standard  has  been  adopted 
at  the  present  time  for  an  asphalt  pavement. 

In  Toronto,  Can.,  by  the  terms  of  an  agreement  between  the 
city  and  the  Toronto  Eailway  Co.,  a  permanent  track-construction 
was  required  whenever  the  streets  should  be  paved  with  a  per- 
manent pavement. 

Fig.  37  shows  a  section  of  a  track  as  per  their  standard  adopted 
in  1892.  The  rail  weighed  73  pounds  per  yard,  but  it  is  said  at 
the  present  time  that  with  their  experience  they  would  now  lay  a 
heavier  rail.  This  was  one  of  the  first,  if  not  the  first,  of  the  attempts 
made  to  lay  street-car  rails  on  a  firm  concrete  base,  and  has  proved 
entirely  satisfactory.  In  the  early  asphalt  pavements  the  space 
between  the  rails  and  tracks  was  paved  with  asphalt,  but  from  the 
experience  there  it  has  been  deemed  best  in  the  future  to  pave  that 
space  with  blocks.  At  first  granite  was  used,  but  so  much  com- 
plaint was  made  by  bicyclists  that  Scoria  blocks  imported  from 
England  were  used  instead.  In  1892  there  were  laid  29.9  miles  of 
single  track,  at  an  expense  of  $322,555;  in  1893,  26.1  miles  of 
single  track,  at  an  expense  of  $392,030;  in  1894,  9.8  miles  of  single 
track,  at  an  expense  of  $116,942.61. 

In  Sioux  City,  la.,  in  1897  street  pavements  of  brick  and  asphalt 
were  ordered  for  streets  in  which  were  located  the  tracks  of  the 
Sioux  City  Traction  Co.  After  studying  the  situation,  the  company 
adopted  the  plan  shown  in  Fig.  38  for  asphalt  pavements.  The 
construction  for  brick  pavements  was  the  same  except  that  the 
groove  was  made  by  a  specially  shaped  brick.  The  company  had 
used  tee  rails  in  some  instances  without  any  objection  being  made, 
and  for  that  reason  6-inch  tee  rails,  60  feet  long,  were  adopted  to 
be  laid  on  steel  ties  spaced  3  feet  from  centre  to  centre.  The  rails 
were  joined  by  26-inch  bolt-spliced  bars  and  separated  by  f  x  11- 
inch  steel  tie-rods,  spaced  7  feet  6  inches  between  centres. 

Under   each   rail   were   laid   continuous   beams    of   Portland- 


THE  CONSTRUCTION  OF  STREET-CAR   TRACKS.        441 


PORTLAND  CEMENT  MORTAR          _  CONCRETE  PORTLAND  CEMENT  &  GRAVEL 


f,,,   NATURAL  CEMENT 
CONCRETE 

/»//  PORTLAND  CEMENT 
CONCRETE 


FIG.  36. 

CEMENT  MORTAR 


GRAVEL 
2"  TILE  PIPK 


FIG.   37. 


FIG.  38. 


442        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

cement  concrete  of  an  average  width  of  15  inches  and  a  depth  of 
9  inches.  At  the  joints  the  rails  rested  upon  a  steel  plate 
f "  x  6"  x  24",  bedded  on  a  concrete  beam.  The  concrete  of  the 
beam  was  formed  of  one  part  of  Portland  cement,  two  and  one- 
half  parts  of  sand,  and  five  parts  of  broken  stone.  On  curves  and 
in  special  work,  instead  of  the  concrete  beam,  oak  ties  were  used 
bedded  in  6  inches  of  concrete  similar  to  that  above  described. 
After  the  subgrade  had  been  prepared  the  rails  were  placed  in 
position,  the  track  made  up,  surfaced,  lined,  and  gauged,  resting 
on  wooden  blocks  placed  under  each  rail  every  8  or  10  feet.  The 
contractor  then  excavated  under  the  rails  and  placed  in  position 
the  wooden  forms  of  the  beams. 

The  concrete  for  the  foundation  of  the  pavement  was  then 
laid  between  the  rails,  being  thoroughly  tamped  up  under  the 
ties  so  as  to  fill  the  corrugations.  After  this  concrete  had  received 
one  day's  set,  the  wooden  forms  were  removed  and  the  concrete 
beam  placed  in  the  trench  which  was  left  for  it,  and  thoroughly 
tamped  up  under  the  rail  so  as  to  cover  the  rail-flange.  The  con- 
crete in  the  beams  was  allowed  to  set  for  eight  days  before  the 
track  was  used. 

During  these  eight  days  the  track  was  naturally  exposed  to 
changes  of  temperature,  and  as  it  was  laid  during  extremely  hot 
weather,  the  temperature  changes  were  extreme  between  day  and 
night.  The  amount  of  expansion  and  contraction  was  found  to 
be  from  3  to  4^  inches  in  400  feet.  In  order  to  protect  the  track 
from  these  changes  in  temperature,  the  rails  were  covered  with 
Y-shaped  troughs  made  from  boards  12  inches  wide  and  7  feet  6 
inches  long,  so  that  the  trough  could  be  set  between  the  tie-rods. 

In  a  brick  pavement  where  sand  was  to  be  used  on  the  foun- 
dation, the  rails  were  covered  with  sand  previous  to  placing  the 
troughs  over  them.  In  the  asphalt  pavement  the  troughs  were 
used  until  the  beam  was  put  in,  when  the  toothing-blocks  were 
laid  as  fast  as  the  beam  was  constructed,  affording  the  same  pro- 
tection from  temperature  as  did  the  sand  on  the  brick  streets. 
This  device  successfully  prevented  any  trouble  from  expansion. 

On  the  brick  streets  on  the  outside  of  the  rails  the  brick  was 
laid  up  close  to  the  head  of  the  rail,  the  space  between  the  two 
flanges  of  the  rail  being  filled  with  cement  mortar,  but  on  the 


I' 

THE  CONSTRUCTION  OF  STREET- CAR  TRACKS,        443 

inside  special  brick  were  provided,  made  of  such  shape  that  they 
would  extend  under  the  head  and  butt  up  tightly  against  the 
flange.  On  the  asphalt  streets  toothing-blocks  were  laid  alternately 
as  headers  and  stretchers,  the  space  between  the  flange  being  filled 
as  before.  On  the  inside,  however,  the  blocks  were  brought  to 
within  1J  inches  of  the  head  of  the  rail,  and  the  space  between  the 
block  and  flange  to  within  1^  inches  of  the  top,  being  filled  with 
cement  mortar,  and  the  space  above  this  cement  mortar  being  filled 
with  specially  prepared  asphaltic  cement,  the  street-car  company 
running  a  car  over  the  track  to  form  a  groove  with  the  flange  of  a 
wheel.  It  is  said  that,  although  this  track  was  laid  in  the  hottest 
weather,  none  of  the  joints  opened  in  the  winter,  and  a  care- 
ful examination  could  discover  only  about  30  per  cent  of  the 
joints. 

The  above  description  was  taken  from  the  Street  Railway  Jour- 
nal for  August,  1898. 

In  March,  1900,  the  general  manager  of  this  road  says:  "We 
have  not  expended  one  penny  in  maintaining  it  since  it  was  put 
in,  and  I  consider  it  as  nearly  a  permanent  roadbed-construction 
as  I  have  ever  seen." 

Fig.  39  shows  the  construction  adopted  by  the  Third  Avenue 


FIG  39. 


Railway  Co.  of  New  York  City  when  it  substituted  electric  trac- 
tion for  cables.  It  is  not  intended  to  show  the  entire  detail  of 
the  -work,  but  only  that  which  would  affect  the  pavement.  It  will 
be  noticed  that  the  rail  is  the  regularly  adopted  Trilby  rail  set  on 


444        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

a  wooden  creosoted  beam.  The  object  of  this  beam  is  to  give  a 
certain  amount  of  elasticity  to  the  track,  so  as  to  make  it  smoother 
and  more  comfortable  to  passengers.  The  yokes  were  spaced  5 
feet  apart  from  centre  to  centre. 

The  above  construction  was  used  on  the  subsidiary  lines,  but 
on  Third  Avenue  proper  the  form  of  the  yoke  was  somewhat 
changed,  and  instead  of  the  creosoted  beam  a  heavy  spring  was 
used  resting  upon  the  yoke,  and  upon  which  the  rail  rested.  This 
spring  is  so  designed  that  when  the  centre  is  depressed  the  ends 
rise,  presenting  a  corrugated  surface  of  such  strength  that  it  is 
estimated  that  it  will  sustain  a  weight  of  from  10,000  to  12,000 
pounds.  The  springs  are  4  inches  wide,  and  the  deflection  at  the 
passage  of  a  loaded  car  carrying  about  6400  pounds  on  each  wheel 
is  about  -^g-  of  an  inch  and  is  noticeable  from  the  street. 

From  a  pavement  standpoint  it  would  seem  that  a  wood  con- 
struction would  be  better  than  the  spring,  especially  if  laid  in  an 
asphalt  pavement,  as  a  real  deflection  of  -g-%  of  an  inch  would 
T)reak  the  joint  between  the  asphalt  and  the  rail  enough  to  per- 
mit the  entrance  of  moisture,  which  would  naturally  lead  to  dis- 
integration. In  Third  Avenue,  however,  the  pavement  outside 
•of  the  track  is  granite  block,  but,  the  space  between  the  conduit- 
slot  and  the  rail  being  so  narrow,  it  was  deemed  best  to  pave  this 
with  asphalt.  Concrete  was  laid  to  within  2  inches  of  the  top  of 
the  rail,  when  about  1  inch  of  asphalt  pavement  was  spread  over 
the  surface  in  which  was  bedded  a  specially  designed  grillwork 
of  f-inch  cast-iron  bars,  forming  squares  about  3J  inches  in  size. 
More  asphalt  was  then  tilled  in  on  top  of  that  first  laid,  in  ana 
around  the  iron,  and  thoroughly  rolled  and  compacted  so  that  its 
finished  surface  was  in  a  straight  line  between  the  slot  and  the 
head  of  the  rail. 

Fig.  40  represents  the  permanent  construction  of  railway- 
tracks  in  an  asphalt  street  in  Detroit,  Mich.  This  shows  the 
space  between  the  tracks  and  rails  paved  with  brick  or  stone 
blocks.  The  special  part  of  this  construction  is  the  tie-bar  which 
is  bolted  to  the  base  of  the  rail,  there  being  no  connection  at  all 
between  the  webs  as  in  the  other  methods  heretofore  shown.  The 
Detroit  Railway  Co.  consider  that  this  method  of  construction  is 
a  success.  While  the  tie  connecting  the  webs  of  the  rail  is  not 


f 

THE  COXSTRUC2IOX  OF  STREET- CAR  TRACKS.        445 

particularly  objectionable  in  an  asphalt  pavement,  as  the  concrete 
is  filled  all  around  it,  it  is  decidedly  so  in  a  stone  block  pavement. 
It  often  happens  that  the  ties  are  not  exactly  square  with  the 


track,  and,  in  any  event,  it  makes  it  necessary  to  use  a  certain 
number  of  courses  of  blocks  between  the  ties,  which  often  makes 
the  joints  wider  than  is  desired. 

Fig.  41  shows  the  tie-construction  in  an  asphalt  pavement  in 
Cincinnati,  0.    This  city  was  one  of  the  first  cities  to  adopt  con- 


8ECTION  THROUGH  TIE 


Fi^.  41. 

crete  construction,  and,  as  is  shown  in  the  cut,  lays  concrete  under 
all  the  ties  and,  in  the  case  of  asphalt,  over  them  as  well,  so  that 
the  tie  is  entirely  surrounded  with  concrete.  Very  satisfactory  re- 
sults have  been  obtained  from  this  kind  of  construction. 

In  the  city  of  Rochester,  N.  Y.,  when  a  street  is  permanently 
paved  the  city  orders  the  street-car  company  to  construct  a  per- 


44:6        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

manent  pavement  between  its  tracks  and  for  a  space  of  2  feet 
outside.  If  the  company  shows  no  disposition  to  do  this,  the  city 
authorities  advertise  the  work  and  have  it  done  under  a  separate 
contract  from  the  pavement  proper,  and  the  expense  of  the  same 
is  charged  to  the  street-railway  company.  While  this  method 
might  bring  about  some  conflict  on  account  of  having  two  con- 
tractors on  the  same  street,  as  a  matter  of  fact  the  work  of  the 
street-railway  company  has  always  been  performed  by  the  same 
contractor  as  the  street  pavement. 

Fig.  42  shows  the  construction  used  in  Eochester  in   1898. 
This  plan  is  peculiar  in  that  the  ties  are  all  made  of  old  rails. 


The  work  was  all  double  track,  and  every  third  tie  was  carried 
across  to  both  tracks;  and  as  the  rails  were  rigidly  bolted  to  the 
ties,  the  entire  work  was  really  one  piece  of  construction.  As  in 
the  Sioux  City  work  previously  described,  the  track  was  gauged, 
lined  up,  and  blocked  up  to  grade  before  any  concrete  work  was 
performed.  The  concrete  between  and  under  the  ties,  as  well  as 
in  the  concrete  beam  under  the  rail,  was  then  laid  and  thoroughly 
tamped  under  and  about  the  old  and  new  rails.  The  concrete  in 
the  track-construction  is  composed  of  one  part  of  Portland 
cement,  three  of  sand,  and  six  of  stone.  This  particular  con- 
struction relates  to  brick  pavement.  Where  wooden  ties  are  used 
instead  of  the  iron  ones  just  described,  the  concrete  extends  under 
and  between  the  ties  as  in  the  Cincinnati  construction. 

Fig.  43  shows  the  Rochester  construction  for  asphalt  with  the 
concrete  beams.    The  space  between  the  rails  is  paved  with  stone 


THE  CONSTRUCTION  OF  STREET-CAR   TRACKS.        447 


blocks,  the  asphalt  being  laid  up  to  the  outside  of  the  rail.  In 
this  instance  the  rails  were  clamped  to  a  concrete  beam  as  shown 
in  Fig.  44,  there  being  three  clamps  to  a  30-foot  rail,  and  five  to 
one  60  feet  in  length.  A  cushion  of  asphalt  mastic  ^  inch  thick 
is  laid  on  top  of  the  concrete  beam  to  make  the  bearing  of  the  rail 
more  elastic.  Attention  is  called  to  the  provision  made  for  drain- 


NATURAL 

CEMENT 
CONCHKTE 


FIG.  43. 


PLATE  12"  x  4"  X  \" 
FIG.  44. 

age,  should  any  water  seep  through  the  joints  of  the  blocks  down  to 
the  sand  cushion.  It  will  be  noticed  that  drain-tiles  are  laid  about 
1  foot  inside  of  the  outside  rails,  in  about  the  same  location  as  in 
the  Toronto  plan. 

In  1897  it  was  necessary  in  an  extension  to  some  street-rail- 
way lines  in  Yonkers,  N.  Y.,  to  construct  a  track  in  an  asphalt 
pavement  already  laid.  In  this  particular  instance  the  concrete 


448        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

beam  was  undoubtedly  the  cheapest.,  as  it  admitted  of  a  track 
being  constructed  with  the  least  disturbance  of  the  pavement. 
Two  channels  to  receive  the  rails  were  cut  in  the  asphalt,  12 
inches  wide  at  the  surface  and  18  inches  at  the  bottom,  a  total 
depth  of  18  inches.  Channels  were  also  cut  transversely  down  to 
the  top  of  the  concrete  beam  for  placing  the  tie-bars,  which  con- 
sisted of  angle-irons  to  which  the  rails  were  bolted.  The  method 
in  detail  is  shown  in  Fig.  45.  In  cutting  through  the  asphalt  it 


[•"'Opening'-*, 


Angle  Bars  10'  Centers 


FIG.  45. 


was  found  cheaper  to  burn  through  the  wearing  surface  with  a 
No.  8  iron  wire,  heated  by  connecting  it  with  the  trolley  wire 
already  erected  overhead,  and  stretching  the  iron  wire  along  the 
lines  marked  for  the  edges  of  the  opening. 


FIG.  46. 

Fig.  46  shows  the  construction  adopted  in  Minneapolis  by  the 
Twin  City  Eapid  Transit  Co.  The  method  of  construction  was 
described  by  Mr.  Cappelen  in  a  discussion  on  the  "  Influence  of 


THE  CONSTRUCTION  OF  STREET- CAR  TRACKS.        449 

Bails  on  Pavement "  before  the  American  Society  of  Civil  En- 
gineers: 

"  The  ties  were  first  laid  on  a  prepared  subgrade  6  to  8  feet 
apart,  and  the  rails  lined  up  and  temporarily  fastened  to  the  ties. 
Cast-iron  joints  were  made  and  a  concrete  beam  put  in  between 
the  ties.  The  ties  were  then  pulled  out  and  the  space  filled  and 
the  balance  of  the  street  concreted.  The  rails  were  also  spiked  to 
the  concrete  beam  as  soon  as  it  was  in  place.  The  track  was  kept 
in  perfect  alignment  in  this  way.  After  discussing  the  work  as 
it  progressed  a  further  modification  in  constructing  the  beam  was 
adopted.  As  it  was  not  always  possible  to  follow  with  the  con- 
crete work  of  the  street  proper  as  fast  as  the  beam  was  built,  a 
good  bond  was  not  obtained  between  the  beam  and  the  other  con- 
crete; so  the  method  was  changed.  The  ordinary  concrete  was 
put  down  outside  and  inside  of  the  rails,  forming  a  rough  groove 
about  8  inches  deep,  15  inches  wide  at  the  bottom,  and  18  to  20 
inches  at  the  top.  In  this  groove  as  soon  as  it  was  built  the  beam 
of  concrete  was  placed.  Otherwise  the  construction  was  as  be- 
fore." 

The  cost  of  this  work  as  stated  by  Mr.  Cappelen  was  about 
$33,908  per  mile  of  double  track,  including  the  asphalt  pavement. 

When  the  street-car  service  of  Dublin,  Ireland,  was  remodelled 
several  years  ago,  the  principle  of  having  the  track-construction  a 
part  of  the  pavement  was  recognized,  and  concrete  was  laid  on  the 
street  as  if  the  pavement  only  were  to  be  laid.  The  rails  were  of 
the  side-bearing  pattern,  7  inches  deep  and  7  inches  wide  at  the 
base,  and  were  laid  directly  on  the  concrete  base  and  the  blocks 
paved  in  about  them. 

The  foregoing  illustrations  of  street-car  track-construction  show 
very  conclusively  that  the  street-railway  companies  realize  and 
understand  that  the  best  method  is  the  most  economical,  and  that 
the  different  companies  are  earnestly  searching  for  what  is  the  best 
method. 

In  determining  the  exact  construction  of  a  street-railway  track 
for  any  street,  there  must  be  taken  into  consideration  the  kind  of 
pavement  to  be  laid,  the  amount  of  traffic  on  the  street,  the  traffic 
of  the  railway,  and  the  power  used  to  propel  the  cars. 

The  kind  of  pavement  on  the  street  will  govern  to  a  certain 


450        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

extent  the  form  of  rail  to  be  used,  and  many  details  of  construc- 
tion if  the  pavement  be  of  asphalt.  The  traffic  of  the  street  will 
be  the  governing  principle  as  to  the  character  of  the  pavement 
next  the  rail.  It  is  a  well-recognized  fact  by  street-railway  offi- 
cials that  when  cars  are  operated  by  external  power,  such  as  cable 
or  animals,  the  wear  and  tear  on  the  track  is  much  less  than  when 
electricity  or  compressed  air  is  used,  on  account  of  the  friction  on 
the  rails.  When  the  wheels  are  turned  by  motors  attached  to  their 
axles,  the  grinding  effect  of  the  wheels  on  the  rails  wears  them 
out  very  materially,  and  much  faster  than  on  a  cable  road.  This 
is  illustrated  very  plainly  by  the  increased  wear  that  is  always, 
noticeable  on  an  up-grade  track  over  the  track  used  by  down-grade 
cars,  especially  where  the  cars  are  moved  by  the  friction  on  the 
rails. 

It  is  extremely  difficult  to  estimate  in  advance  the  life  of  the 
rail  of  a  street-railway.  It  is  generally  measured  by  the  number 
of  cars  passing  over  it.  Some  engineers  give  as  the  average  life 
of  the  ordinary  steel  rail  the  passage  of  6,000,000  cars  over  it.  On 
a  track  laid  in  Brooklyn,  on  Fulton  Street  between  Brooklyn 
Bridge  and  the  City  Hall,  in  1895,  the  rails  were  renewed  in  1899. 
The  traffic  on  this  piece  of  track  has  been  estimated  for  that 
period  as  being  one  car  for  every  fifty  seconds  during  twenty-four 
hours.  This  would  mean  the  passage  of  2,522,880  cars  over  the 
track  before  it  was  renewed.  It  is  stated  that  after  2,500,000  cars 
had  passed  over  the  tracks  of  the  Third  Avenue  Railroad  in  New 
York  City  the  rails  were  appreciably  worn  and  hollowed  out  in 
some  instances,  although  the  road  was  operated  by  cable  and  the 
track  was  solidly  and  substantially  built. 

Mr.  Owen,  in  a  paper  before  the  American  Society  of  Civil 
Engineers,  gives  as  the  approximate  life  of  a  rail  ten  years,  and 
Mr.  Bowen,  in  a  paper  presented  to  the  American  Street  Railway 
Association  in  October,  1896,  estimated  that  the  rails  of  a  cable- 
track  in  State  Street,  Chicago,  would  last  twelve  years. 

In  all  of  these  cases  the  rails  would  require  renewing  before 
any  improved  pavement  would  be  relaid,  provided  that  both  con- 
structions were  carried  out  at  the  same  time,  so  that  a  construc- 
tion should  be  adopted  that  would  provide  for  the  renewal  of  the 
rails  at  the  least  possible  expenditure  of  labor. 


.  f 

THE  CONSTRUCTION  OF  STREET- CAR  TRACKS.        451 

One  of  the  great  sources  of  trouble  to  any  car-track,  whether 
operated  by  steam  or  electricity,  is  at  the  joints  of  the  rails.  A  great 
many  devices  have  been  employed  for  the  purpose  of  making  these 
joints  as  nearly  perfect  and  as  much  like  the  remainder  of  the  rail  as 
possible.  How  important  this  is  can  be  understood  by  another  state- 
ment by  Mr.  Bowen  in  the  paper  previously  referred  to,  in  which 
he  says  that  when  the  question  came  before  him  of  renewing  the 
State  Street  track  in  Chicago,  he  had  a  car  weighing  over  four 
tons  run  over  it,  attached  to  a  grip-car  by  means  of  a  dynamom- 
eter. The  same  car  was  run  over  a  track  newly  laid  and  at  the 
same  speed  as  over  the  old  line.  The  dynamometer  showed  that 
it  took  13.75  pounds  more  pull  per  ton  to  haul  the  car  over  the 
old  line  than  over  the  new.  That  he  attributed  a  great  deal  olf 
this  extra  power  required  to  the  condition  of  the  track  at  the 
joints  can  be  seen  from  his  conclusion  that  a  new  track  with  cast 
joints  would  last  twelve  years,  and  as  there  will  be  no  low  joints, 
the  draw-bar  pull  will  not  increase  much  until  the  rail  is  worn 
down  sufficiently  to  allow  the  wheel  to  run  on  the  flange. 

When  it  is  remembered  that  some  engineers  figure  that  the 
force  required  to  haul  a  ton  on  a  well-constructed  track  -should 
not  exceed  8  pounds,  the  effect  of  the  track  being  in  bad  condition 
can  be  plainly  understood. 

This  trouble  to  joints  has  been  obviated  to  a  great  extent  by 
the  recent  practice  of  increasing  the  length  of  the  rails  from  30 
to  60  feet.  This  reduces  the  number  of  joints  one-half  at  once, 
and  the  average  cost  per  rail  is  increased  only  about  $2  per  ton  by 
extra  length.  Since  electricity  has  been  so  generally  introduced 
upon  street  railways  as  a  motive  power,  and  the  rails  have  been 
used  as  a  return  conductor  for  the  electricity,  a  great  deal  of  at- 
tention has  been  paid  to  the  joints.  What  is  known  as  the  cast- 
iron  joint  has  been  used  with  good  success.  This  joint  has  been 
described  in  Mr.  Bowen' s  paper  as  follows: 

"  The  rails  at  the  joint  are  scraped  and  brightened.  A  cast- 
iron  mould  is  placed  around  the  joint,  making  a  tight  fit.  Into 
this  molten  iron  25  per  cent  scrap,  25  per  cent  soft  and  50  per 
cent  hard  silicious  pig  iron  is  poured.  The  metal  in  contact  with 
the  mould  begins  to  cool  and  form  a  crust,  while  the  interior  re- 
mains molten.  This  crust  continues  to  cool  and  at  the  same  time 


452        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

contracts,  forcing  the  molten  metal  strongly  towards  the  centre, 
which  makes  a  solid  and  rigid  joint.  The  top  and  bottom  part  of 
the  ball  of  the  rail  is  afterwards  filed  off  perfectly  level,  so  that  it 
is  very  difficult  to  detect  the  joint  by  riding  over  it  or  looking  for 
it.  Upon  breaking  the  joint  which  has  been  cast  welded,  three 
spots  will  usually  be  found  where  amalgamation  has  -taken  place 
between  the  rail  and  the  cast  portion,  one  on  each  side  of  the  web 
of  the  rail,  and  the  other  on  the  bottom." 

He  says  that  17,000  joints  were  made  in  Chicago  during  the 
year  1895,  and  of  these  only  154  were  lost,  and  that  the  joint  in 
comparative  tests  has  been  shown  to  be  far  stronger  than  the  rail 
itself,  and  that  breakages  that  have  occurred  were  due  to  flaws  in 
the  metal.  The  metal  cast  around  the  joint  has  eight  times  the 
cross-section  area  of  the  rail.  Therefore,  if  the  cast  iron  has  one- 
fourth  the  strength  of  steel,  the  joint  will  be  twice  as  strong  as 
the  rail. 

In  Brooklyn,  N.  Y.,  1600  of  these  cast  joints  were  made  in 
1896,  and  only  one  failed  during  the  first  six  months.  In  2000 
joints  made  by  another  company  forty  had  broken. 

Another  method  of  welding  rails  has  been  described  under 
"  The  Method  of  Track  Construction  in  ^Buffalo."  It  was  con- 
sidered doubtful  by  many  engineers  whether  such  construction 
would  be  successful  on  account  of  its  expansion  and  contraction 
due  to  changes  in  temperature,  but  it  would  seem  from  the  few 
failures  that  not  as  great  changes  in  temperature  occurred  as  was 
expected.  This  is  due  doubtless  to  the  rail  being  almost  entirely 
surrounded  by  the  pavement,  preventing  any  direct  action  of  the 
sun  and  keeping  the  greater  part  of  the  rail  at  the  temperature  of 
the  pavement,  so  that  no  buckling  has  occurred  on  account  of  the 
heat,  and  that  the  elasticity  of  the  rail  or  joint  has  been  sufficient 
to  take  up  the  contraction  due  to  cold  weather.  At  all  events, 
there  seems  to  have  been  no  trouble  on  that  account  from  changes 
of  temperature. 

Coming  now  to  the  discussion  of  what  is  the  best  construction 
for  a  railway  track  in  different  improved  pavements,  Fig.  47  will 
show  the  method  which  the  author  would  recommend  for  a  street 
to  be  paved  with  granite.  The  rail  is-  that  shown  in  either  Fig.  28 
or  Fig.  29,  as  may  be  deemed  best  by  local  authorities.  The  ties 


f 

THE  CONSTRUCTION  OF  STREET-CAR  TRACKS.        453 

should  be  of  steel,  spaced  10  feet  apart  and  of  the  kind  shown 
in  either  the  Sioux  City  or  Yonkers  construction,  and  rest- 
ing on  top  of  a  concrete  beam,  there  being  no  connection  what- 
ever between  the  web  of  the  rails.  The  objection  urged  to  this 
method,  that  the  rails  cannot  be  kept  in  gauge,  does  not  seem 


FIG.  47. 

valid  when  it  has  been  used  successfully  by  many  companies,  and 
when  with  the  ordinary  wooden-tie  construction  the  tie  is  simply 
held  to  gauge  by  spikes  on  the  bottom  flange.  With  the  method 
proposed,  and  a  solid  granite  pavement  built  tight  against  the  rail, 
it  would  seem  that  no  difficulty  would  be  encountered  in  keeping 
the  rails  to  line  and  gauge. 

Fig.  48  shows  the  plan  proposed  for  the  construction  on  a  street 


U  — 


FIG.  48. 

paved  with  asphalt.     The  rail  is  the  same  shape  as  that  recom- 
mended for  granite,  except  that  it  is  but  6  inches  deep.    The  rail 


454        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

can  be  made  of  any  required  area  to  give  the  necessary  strength, 
and  the  metal  can  be  used  to  better  advantage  on  a  shallow  rail, 
and  with  asphalt  as  great  depth  is  not  required  as  when  granite 
block  is  laid.  The  arrangement  of  ties  would  be  the  same  as  in  the 
other  case,  except  that  if  the  street-railway  authorities  have  any 
preference  for  a  tie  from  web  to  web  of  the  rails,  there  would  be  no 
objection,  as  the  concrete  base  for  the  asphalt  can  be  laid  around 
the  ties  without  any  difficulty. 

There  is  considerable  difference  in  the  practice  of  different  en- 
gineers as  to  whether  asphalt  should  be  laid  up  to  the  rails  or 
whether  blocks  of  some  kind  should  be  used.  This  will  depend  to 
a  great  extent  upon  the  conditions  of  the  street  traffic.  If  the 
traffic  be  light,  and  the  above  construction  is  used,  there  can  be  no 
objection  to  finishing  with  asphalt  up  to  the  rails.  Great  care,  how- 
ever, must  be  exercised  in  doing  this,  and  the  asphalt  should  be 
tamped  solidly  under  the  lip  and  head  of  the  rail,  so  that  if  wheels 
run  along  next  to  the  rail,  the  asphalt  will  be  sufficiently  strong  to 
resist  the  tendency  to  rut.  In  some  cities,  however,  the  entire  space 
between  the  tracks  and  rails  is  paved  with  stone  blocks,  as  many  en- 
gineers think  that  this  is  a  better  construction.  That  it  is  more 
•economical  is  probably  true;  but  if  the  street  be  comparatively 
narrow,  only  a  small  portion  of  the  street  will  be  paved  with  asphalt 
if  all  of  the  track-space  is  paved  with  stone.  In  some  streets  also 
it  is  considered  necessary  to  lay  blocks  of  stone  or  brick  on  the 
•outside  of  the  rail  as  well  as  inside,  and  where  the  street-traffic 
is  heavy  this  may  be  advisable.  It  should  be  remembered,  however, 
that  the  theory  of  this  construction  of  stone  or  brick  is  to  prevent 
the  tendency  of  the  wheels  to  rut  the  pavement  alongside  the  rails; 
but  if,  in  the  construction  of  a  track,  a  rail  is  used  that  will  present 
practically  the  same  surface  to  traffic  as  the  remainder  of  the  street, 
neither  inviting  nor  repelling  wheels,  this  tendency  is  materially 
reduced. 

The  recommendation,  however,  would  be,  on  streets  of  moder- 
ately heavy  traffic,  to  place  a  row  of  toothing-stones  arranged  in 
pairs  and  set  as  headers  on  the  inside  of  the  rail,  and  on  the  out- 
side lay  the  asphalt  next  to  the  rail.  If  the  distance  between  the 
•curbs  is  so  wide  that  there  is  plenty  of  room  outside  of  the  track 
lor  the  street-travel,  and  the  street-railway  authorities,  for  economi- 


TUE  CONSTRUCTION  OF  STREET-CAR   TRACKS. 


455 


cal  reasons,  wish  to  lay  stone  or  brick  pavement  between  the  rails, 
there  would  be  no  particular  objection  if  it  be  done  in  a  thorough 
and  substantial  manner. 

Fig.  49  represents  a  recommendation  for  a  brick  pavement. 
This  is  substantially  the  same  as  that  shown  in  Fig.  48,  except 
that  no  tie-rods  should  be  used  between  the  rails  but  at  the  base 
upon  the  concrete  beam  as  recommended  for  granite.  It  is  very 
difficult  in  using  tie-rods  between  the  webs  to  so  place  the  holes 
that  the  rods  will  be  exactly  perpendicular  to  the  rails,  and 


_J 


FIG.  49. 

trouble  always  occurs  in  laying  the  blocks,  whether  of  stone  or 
brick,  between  these  bars  on  that  account.  It  also  makes  an  extra- 
wide  joint  wherever  these  rods  occur,  and  satisfactory  results  can 
never  be  obtained  in  that  way. 

The  space  between  the  upper  and  the  lower  flange  of  the  rail, 
on  the  outside  and  on  the  inside,  must  be  filled  when  a  block  pave- 
ment of  any  kind  is  to  be  used.  Untreated  and  creosoted  wood, 
sand,  cement  mortar,  and  specially  burned  tiling  have  been  used 
for  this  purpose.  Wood  is  probably  the  cheapest,  and  if  the  track 
is  to  sustain  heavy  traffic,  so  that  it  will  require  renewal  every  five 
or  six  years,  untreated  wood  will  probably  be  satisfactory;  but  if  it 
is  to  remain  ten  or  twelve  years,  it  should  be  creosoted,  so  as  to 
prevent  decay  before  the  rails  will  require  renewing.  Cement 
mortar  gives  good  results,  but  is  considered  expensive  and  can  be 
used  but  once.  Specially  burned  bricks  have  been  used  with  good 
results,  although  some  engineers  object  to  them  on  account  of  their 
being  easily  crushed. 


456        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Whatever  material  is  used  for  this  filling,  the  space  between  it 
and  the  blocks  and  rails  should  be  completely  filled  with  the  same 
filler  as  that  used  in  the  block  pavement.,  whether  paving-cement 
or  cement  grout,,  so  as  to  prevent  the  admission  of  water  around  the 
rail.  Whatever  the  block  construction  is  next  to  the  rail,  whether 
stone  or  brick,  or  whether  used  in  the  entire  pavement  or  only  as 
a  protection  to  the  asphalt  next  to  the  rail,  the  blocks  should  be 
bedded  firmly  in  good  cement  mortar  resting  on  a  concrete  base, 
so  that  they  will  remain  firmly  in  place  without  any  settlement 
under  travel  and  be  as  rigid  as  the  rail  itself. 

If  it  be  desired  to  use  the  wooden-tie  construction  instead  of 
any  of  the  methods  shown  above,  the  ties  should  be  laid  on  a  con- 
crete base  and  the  space  between  and  around  them  filled  with  con- 
crete to  the  required  height  for  the  base  of  the  pavement.  In  such 
a  case,  where,  in  asphalt  and  in  brick  pavements,  the  ties  would  be 
almost  if  not  entirely  surrounded  with  concrete,  it  would  doubtless 
be  more  economical  to  use  a  creosoted  tie  rather  than  an  untreated 
one,  so  as  to  prevent  the  tearing  up  of  the  concrete  to  renew  the 
ties,  as  the  untreated  tie  would  require  renewal  much  oftener  than 
the  treated  one.  The  extra  expense  involved,  assuming  the  cost 
of  creosoting  to  be  25  cents  per  tie,  would  be  about  $700  per  mile 
of  single  track,  but  under  the  conditions  mentioned  above  this  ex- 
pense would  be  justifiable. 

If  it  be  necessary  to  lay  a  street-car  track  in  the  middle  of  a 
macadam  road  or  a  macadamized  street,  the  best  results  would  be 
obtained  by  the  method  recommended  for  stone  pavements,  the 
space  between  the  tracks  and  rails  being  paved  substantially  with 
stone. 

In  the  suburbs  of  Boston  are  a  great  many  macadamized  streets 
upon  which  street-railways  are  operated.  In  all  of  these  the  track- 
space  is  paved  with  stone,  as  well  'as  from  12  to  18  inches  outside. 
On  a  road,  however,  upon  which  there  is  not  much  travel  good  re- 
sults have  been  obtainerd  by  laying  the  tee  rails  with  the  ordinary 
tie-construction.  The  flange  of  the  wheel  maintains  for  itself  a 
groove  along  the  rail.  While  this  will  probably  require  some  atten- 
tion, especially  for  maintenance  between  the  rails,  it  will  in  the 
end  give  very  satisfactory  results. 

It  seems  almost  impossible,  however,  to  keep  light  teams  out- 


THE  CONSTRUCTION  OF  STREET-CAR  TRACKS.        457 

side  the  tracks  even  on  a  macadam  street;  so  where  the  street- 
traffic  is  considerable,  the  best  method  is,  as  has  been  stated,  to- 
pave  the  track-space  with  stone. 

It  often  happens  that  it  becomes  necessary  to  lay  improved 
pavement  on  a  street  where  a  street-car  track  already  exists  and  in 
good  condition,  with  rails  similar  to  that  shown  in  Fig.  27.  In 
such  cases  the  pavement,  whatever  its  nature,  should  be  laid  be- 
tween rails  on  the  same  level  as  the  head  of  the  rail.  Otherwise 
the  surface  will  be  bad  for  vehicles  crossing  the  track.  In  order 
to  accomplish  this  without  relaying  the  track  with  a  grooved  rail, 
it  will  be  necessary  to  lay  some  foreign  material  next  to  the  rail  to 
form  a  groove. 

A  device  to  accomplish  this,  shown  in  Fig.  50,  has  been  patented 


FIG.  50. 

by  Mr.  Buckland  in  Springfield,  Mass.  It  consists,  as  is  shown 
in  the  figure,  of  cast-iron  blocks  made  to  fit  over  the  tram  of  the 
rail,  and  in  such  shape  as  to  form  the  required  groove.  This  costs 
about  $2500  per  mile  of  track,  and  is  said  to  have  given  good  satis- 
faction where  it  has  been  used. 

When  brick  is  used  for  the  paving  material,  specially  moulded 
blocks  have  been  used  both  on  the  outside  and  inside  of  the  rails. 
When  asphalt  is  used  for  the  paving  material,  granite  toothing- 
blocks  can  be  successfully  employed  by  setting  them  as  headers 


458        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 


against  the  rail,  as  heretofore  recommended,  and  bedding  them 
solidly  with  cement  mortar. 

In  Glasgow,  Scotland,  where  paving  material  of  any  kind  is 
laid  against  the  track  on  each  side  of  the  rail,  alternating  with  the 
blocks  is  laid  a  chilled-steel  block  casting,  4£  inches  square,  and 
roughened  on  top  so  as  to  give  a  foothold  to  horses.  The  block  is 
cast  hollow  in  order  to  save  material,  and  the  alternating  stone 
block  is  of  the  regular  size  as  that  used  on  the  rest  of  the  street. 
This  with  the  rail  gives  a  solid  and  unyielding  bearing  to  wheel- 
traffic,  and  absolutely  prevents  any  ruts  forming  next  to  the  rail. 

Of  what  importance  the  subject  of  track-construction  is  can 
be  seen  from  Table  No.  71,  taken  from  a  report  made  to  the 
Massachusetts  Legislature  in  1898,  which  shows  the  mileage  of 
street-railways  in  the  principal  cities  of  this  country  and  com- 
pared with  those  of  Europe  of  about  the  same  population. 

TABLE  No.  71. 

United  States  Cities.  Miles. 

New  York  City 461 

Chicago 1012 

Philadelphia 502 

Brooklyn 512 

St.  Louis 350 

Baltimore 391 

Boston 452 

Cleveland 335 

Cincinnati 295 

San  Francisco 271 

Pittsburg 305 

Buffalo , 150 

Detroit 221 

Washington 157 

New  Orleans. .  .  209 


European  Cities. 

Paris 206 

Berlin 272 

Vienna 166 

St.  Petersburg 81 

Liverpool 66 

Brussels 82 

Madrid 36 

Dublin.. 82 

Lyons , . .  66 

Amsterdam 82 

Leeds 22 

Dresden 38 

Leipsic 99 

Rome 18 

Copenhagen 40 


According  to  the  Street  Raihvay  Journal  there  were  19,213 
miles  of  street-railways  in  the  United  States  on  Jan.  1,  1900, 
17.969  miles  of  which  were  operated  by  electricity. 


CHAPTER    XIV. 

WIDTH    OF    STREETS    AND    ROADWAYS,    CURBING,    SIDEWALKS, 
GRADES,    ETC. 

• 

WHAT  has  been  said  in  these  pages  heretofore  has  had  special 
reference  to  that  portion  of  the  street  between  the  curbs  and 
wholly  in  regard  to  use,  not  taking  into  consideration  the  general 
appearance  of  the  street.  The  space  between  the  curb  and  the 
property  line,  however,  has  as  much  to  do  with  the  general  effect 
of  the  street,  especially  in  villages  and  suburbs,  as  the  pavement 
itself. 

What  is  the  proper  width  of  streets  has  been  an  open  question 
for  many  years,  and  it  cannot  be  definitely  settled  as  a  rule,  but 
the  width  must  be  governed  by  special  conditions  in  each  case. 
The  east  and  west  streets  of  New  York  City  generally  are  60  feet 
wide,  while  the  avenues  running  north  and  south  are  100  feet 
wide.  In  Brooklyn  the  width  varies  from  40  to  100  feet  accord- 
ing to  locality.  In  Omaha,  Neb.,  the  streets  in  the  original  city 
plat  were  100  feet  wide,  with  two  streets  leading  from  the  capitol 
120  feet  wide.  Macon,  Ga.,  probably  has  the  widest  streets  of  any 
city  in  the  country,  those  running  in  one  direction  being  alter- 
nately 120  feet  and  180  feet  wide.  These  widths  are  extreme  and, 
while  adding  greatly  to  the  beauty  of  the  city,  are  expensive  when 
they  require  paving,  and  inconvenient  in  the  business  part  of  the 
city. 

Broad  Street,  Newark,  N.  J.,  is  132  feet  wide,  with  a  92-foot 
paved  roadway. 

The  distance  between  the  curbs  must  be  established  accord- 
ing to  the  width  of  the  street,  the  amount  of  traffic,  and  whether 
the  roadway  is  to  be  occupied  by  street-car  tracks.  Different  cities 
have  different  principles  for  establishing  these  widths;  some  hav- 
ing a  general  rule  that  applies  to  all  streets,  others  establish  an 
arbitrary  roadway  for  streets  of  different  widths. 

459 


460        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

In  the  old  city  of  Brooklyn,  N".  Y.,  streets  50  feet  wide  had  a 
roadway  of  24  feet,  those  60  feet  wide  a  roadway  of  30  feet,  those 
70  feet  wide  a  roadway  of  34  feet,  those  80  feet  wide  a  roadway  of 
42  feet,  and  those  100  feet  wide  a  roadway  of  60  feet. 

In  New  York  City  the  roadway  of  a  street  60  feet  wide  is  30 
feet.  In  St.  Louis  a  street  60  feet  wide  has  a  roadway  of  36  feet. 
Omaha  and  some  cities  of  Europe  establish  the  width  of  roadway 
as  -equal  to  three-fifths  of  the  entire  width  of  the  street. 

While  it  is  well,  perhaps,  to  establish  these  widths  arbitrarily, 
it  will  often  be  found  best  to  modify  the  rules  according  to  special 
conditions  in  many  cases.  On  a  business  street  a  roadway  should 
be  made  of  such  a  width  as  will  accommodate  traffic,  unless  by  so 
doing  the  sidewalk  space  is  too  much  restricted.  When  car-tracks 
exist  on  such  a  street  the  space  between  the  track  and  curb  should 
loe  of  sufficient  width  to  allow  teams  to  pass  between  the  car  and 
another  team  standing  by  the  curb.  To  accomplish  this  would 
require  a  width  of  roadway  of  about  44  feet.  If  this  width  cannot 
T^e  obtained  without  making  the  sidewalks  too  narrow,  but  one 
track  should  be  allowed  on  the  roadway,  the  cars  making  their 
return-trip  on  another  street.  This  plan  has  been  adopted  for 
Philadelphia  where  the  roadways  of  the  streets  are  very  narrow. 

A  street  70  feet  wide  would  allow  the  above  space  of  44  feet 
for  the  roadway  and  leave  13  feet  on  each  side  for  sidewalks.  In 
cities  of  ordinary  size  this  would  be  sufficient,  and  having  a  street 
of  that  width,  such  an  arrangement  would  give  good  satisfaction. 
In  the  residence  portion  of  the  city  such  width  is  not  necessary 
and  perhaps  not  desirable.  It  has  been  customary  in  most  cities, 
•especially  where  the  property  is  built  up  in  solid  blocks  on  the 
street-line,  to  allow  a  certain  amount  of  space  adjoining  the  prop- 
erty to  be  used  and  fenced  in  by  citizens  as  a  courtyard.  This 
allows  the  building  to  be  constructed  on  the  property-line  and 
liave  a  small  amount  of  yard-space  in  front.  Where  houses  are 
Tyuilt  with  basements  this  is  almost  absolutely  necessary.  As  the 
«xtra  width  of  the  street  over  what  is  necessary  for  roadway, 
street,  and  sidewalk  travel  is  only  required  to  give  light  and  air, 
such  use  can  do  no  harm. 

The  original  practice  in  laying  out  roadways  of  streets  was  to 
make  them  wide,  and  in  most  cases  wider  than  necessary.  Before 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC.  461 

the  time  of  pavements  this  was  not  so  objectionable;  but  when 
the  street  comes  to  be  improved,  any  portion  that  is  paved  over 
and  above  what  is  necessary  for  the  convenience  and  use  of  the 
travelling  public  is  wasted  and  can  better  be  used  for  the  adorn- 
ment of  the  street. 

As  a  general  rule,  it  can  be  laid  down  that  the  width  of  30 
feet  between  curbs  is  sufficient  for  the  ordinary  residence  street. 
When  a  street  or  avenue,  however,  is  or  becomes  a  great  artery  of 
travel,  so  that  it  receives  abnormal  traffic,  then  the  width  should 
be  increased.  A  great  many  streets  in  Brooklyn,  N.  Y.,  are  only 
34  feet  wide  between  curbs,  and  have  on  them  a  double  line  of 
street-car  tracks.  This  leaves  a  space  of  only  9£  feet  between  the 
tracks  and  curb.  This  seems  small,  but  when  the  street  is  paved 
with  smooth  pavement  and  the  street-car  tracks  are  properly  con- 
structed it  serves  very  well  in  the  ordinary  residence  street. 

Where  streets  are  of  great  width,  as  in  some  of  those  pre- 
viously cited,  parks  are  often  laid  out  in  the  centre  of  the  street, 
thus  reducing  the  amount  of  area  to  be  paved  and  at  the  same 
time  adding  very  much  to  the  general  appearance  of  the  street 
and  city.  In  the  180-foot  streets  of  Macon  before  mentioned,  the 
space  was  divided  up  into  15  feet  for  sidewalk,  a  50-foot  roadway, 
a  park  50  feet  wide  in  the  centre,  another  50-foot  roadway,  and 
the  other  sidewalk,  15  feet  wide.  These  parks  were  set  out  with 
live-oak  trees  and  added  very  much  to  the  beauty  of  the  city;  but 
even  with  that  arrangement  it  left  a  space  100  feet  wide  to  be 
paved.  Many  of  the  streets  and  parkways  of  Boston,  Baltimore, 
and  other  cities  are  laid  out  in  this  way. 

Ocean  Parkway  in  Brooklyn,  which  extends  from  Prospect  Park 
to  Coney  Island  and  is  the  popular  and  fashionable  drive  of  the 
city,  is  210  feet  wide,  divided  up  as  follows:  Sidewalk,  15  feet; 
roadway  for  heavy  traffic,  25  feet;  park,  30  feet  wide;  roadway, 
70  feet  wide;  another  park,  30  feet  wide;  another  driveway  for 
heavy  traffic  in  the  opposite  direction  from  the  first,  25  feet  wide; 
another  sidewalk,  15  feet  wide.  This  boulevard  has  at  its  upper 
end  eight  rows  of  trees  and  presents  a  very  fine  appearance. 

Having  settled  upon  the  amount  of  space  to  be  left  between  the 
curb-line  and  private  property,  it  remains  to  determine  how  this 
shall  be  treated.  An  ordinance  governing  the  widths  of  courtyards 


462        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

in  the  old  city  of  Brooklyn  provided  that  they  should  be  one- 
twelfth  the  width  of  the  street,  but  not  to  exceed  5  feet.  A  street 
70  feet  wide  having  a  roadway  34  feet  in  width  allows  a  sidewalk- 
space  of  18  feet  on  each  side;  deducting  from  this  5  feet  for  the 
courtyard,  there  is  left  a  space  of  13  feet  to  be  treated. 

The  best  and  probably  the  most  economical  method  of  treating 
this  space  would  be  laying  a  sidewalk  8  feet  wide  next  to  the  court- 
yard, leaving  a  space  of  5  feet  adjacent  to  the  curb,  the  sidewalk 
being  extended  to  the  curb  opposite  every  house  to  give  access  to- 
carriages.  The  remaining  space  could  then  be  sodded  and  would 
give  ample  room  for  the  planting  of  trees,  than  which  nothing  adds 
more  to  the  beauty  of  any  city. 

In  smaller  cities  and  in  the  suburbs  of  large  ones  where  de- 
tached houses  are  built  and  set  well  back  from  the  street-line,. 
courtyards  are  not  necessary,  but  the  location  of  sidewalk  given 
above  would  be  satisfactory.  In  some  localities,  however,  it  might 
be  as  well  to  reduce  the  width  of  sidewalk,  but  in  any  event  it 
should  not  be  allowed  to  be  decreased  beyond  5  feet. 

Some  people  advocate  the  laying  of  the  sidewalk  next  to  the 
curb.  This  plan,  while  sometimes  adopted,  does  not  give  as  good 
satisfaction  as  the  one  proposed,  and  compels  the  trees  to  be  set 
back  at  a  considerable  distance  from  the  curb.  Ocean  Avenue, 
Brooklyn,  is  100  feet  wide  in  the  best  residential  section  of  the 
suburbs  of  Brooklyn,  and  was  recently  improved  and  a  sidewalk  laid 
8  feet  wide  next  to  the  curb.  This  was  considered  best,  not  be- 
cause the  most  desirable  location  for  the  walk,  but  if  located 
further  from  the  curb  it  would  have  destroyed  a  great  many  fine 
trees  that  had  already  attained  considerable  growth  on  a  portion  of 
the  street,  and  the  desire  to  have  the  improvement  uniform  led  to. 
the  adoption  of  the  plan  described. 

Curbing. 

The  curb  of  the  street  adds  very  much  to  its  general  appearance.. 
It  is  practically  placing  the  frame  around  the  picture.  It  acts, 
too,  as  one  side  of  the  gutter  and  serves  to  protect  the  sidewalk- 
space  from  the  wheels  of  carriages  and  delivery-wagons.  Curbing 
is  generally  made  of  granite,  sandstone,  limestone,  and  Portland- 


f 

WIDTH  OF  STREETS  AND  ROADWAYS,  ETC.  463 

cement  concrete,  and  sometimes  even  wood.  This  latter  material 
is  extremely  temporary  and  is  so  seldom  used  that  it  cannot  be 
strictly  considered  curbing  material. 

Dimensions. — In  making  specifications  for  curbing,  the  maxi- 
mum and  minimum  of  length  is  generally  specified.  If  the  stones 
be  too  short,  the  joints  are  frequent  and  the  general  appearance  of 
the  street  thereby  injured.  If  they  are  too  long,  they  are  handled 
and  set  with  difficulty  and  seldom  get  a  firm  bearing  in  their  bed 
and  are  consequently  very  easily  broken.  Their  depth  depends  very 
much  upon  the  material  and  manner  in  which  they  are  set.  The 
extremes  are  from  8  to  30  inches,  although  most  cities  specify  a 
depth  of  from  18  to  20  and  a  few  24  inches.  If  the  street  is  to 
be  paved  with  asphalt  or  brick  and  curb  set  in  concrete,  there  is  no 
necessity  of  making  the  depth  more  than  15  inches,  as  the  concrete 
practically  becomes  a  part  of  the  curb  as  far  as  its  stability  is  con- 
cerned, and  the  firm,,  solid  pavement  in  front  keeps  the  curb  abso- 
lutely in  position. 

With  stone  pavements,  while  the  blocks  run  6  and  8  inches  in 
depth,  a  deeper  curb  will  be  required,  general  practice  making  it 
18  or  20  inches.  In  determining  the  thickness  of  the  curb,  con- 
sideration should  be  given  to  its  appearance  as  well  as  its  useful- 
ness. In  a  residence  street  a  curb  4  inches  thick  would  perhaps  be 
as  wide  as  would  be  necessary  for  use,  but  its  appearance,  especially 
if  the  roadway  should  be  wide,  would  be  bad,  and  the  usual  practice 
is  to  make  the  minimum  width  5  inches.  On  a  business  street 
where  heavy  trucks  are  liable  to  be  backed  up  against  the  curb,  a 
'heavier  stone  is  required  and  one  6  or  7  inches  thick  is  generally 
used. 

On  some  streets  in  Boston  a  granite  curb  is  seen  12  and  even  18 
inches  thick.  This  latter  is,  however,  extreme,  and  in  such  cases  the 
stone  can  be  more  properly  considered  as  a  coping-stone  for  the 
area  wall  than  as  curbing. 

Material. — The  exact  material  that  should  be  used  for  curbing 
depends  much  upon  the  availability  of  any  particular  stone.  For  a 
business  street  granite  is  unquestionably  the  best.  It  presents  a 
good  appearance  even  when  roughly  dressed,  and  will  withstand  the 
blows  which  it  receives  from  heavy  trucks.  While  often  expensive 
in  some  cities,  in  others  it  is  perhaps  as  often  the  cheapest  and 


464        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

most  available  material.  In  cities  near  granite-quarries,  and  where 
the  cost  of  transportation  is  light,  it  is  very  generally  used.  While 
prices  vary  according  to  the  times,  locality,  and  condition,  it  was 
stated  by  the  City  Engineer  of  Albany  that  granite  curbing  in  that 
city  in  1897  cost,  set,  39  cents  per  lineal  foot  for  straight  curb, 
and  in  1898  52J  cents  per  lineal  foot.  Very  few  cities,  however, 
can  get  this  material  for  that  price.  These  stones  were  6  inches 
thick  and  12  inches  deep. 

Hudson  Eiver  bluestone,  which  is  found  in  such  great  quantities 
In  eastern  New  York,  has  been  used  to  a  great  extent  in  New  York, 
Brooklyn,  and  other  neighboring  cities.  It  is  hard,  durable,  and, 
being  stratified,  is  easily  gotten  out  in  any  required  dimension.  In 
cities  in  western  New  York,  and  in  Ohio,  Medina  as  well  as  Berea 
sandstone  has  been  used  very  successfully  for  curbing.  The  latter  is 
soft  when  first  gotten  out  and  is  easily  cut,  but  hardens  under  the 
action  of  the  weather,  and  makes  a  very  satisfactory  material  for 
residence  streets.  Colorado  and  other  sandstones,  as  well  as  granite, 
is  used  in  other  cities  of  the  West  and  South. 

Dressing. — In  specifying  'how  curbing  shall  be  cut,  it  is  custom- 
ary to  designate  it  as  4-,  6-,  or  8-axe  work,  as  the  case  may  be.  This 
me-ans  in  each  case  that  the  axe  shall  have  that  number  of  cutting 
edges  per  inch,  that  is,  the  axe-work  is  produced  by  dressing  the 
stone  with  an  axe  that  has  six  cutting  edges  per  inch.  In  some 
portions  of  the  country  the  softer  stone  is  often  dressed  by  ma- 
chinery. Some  engineers  object  to  this,  because  ordinary  curbing 
is  liable  to  be  chipped  by  traffic,  and,  if  too  smooth,  at  first  any 
defect  will  show  very  plainly  in  contrast  with  the  smooth  surface. 
This,  however,  does  not  seem  to  be  a  valid  objection,  as  instances 
of  injury  are  so  rare  that  it  hardly  seems  that  too  smooth  face  or 
head  of  the  curb  could  be  objected  to.  Granite,  however,  does  not 
require  a  smooth  surface  to  give  it  a  good  appearance. 

Setting. — Curbing  is  generally  set  with  a  slight  batter,  so  that 
it  is  necessary  to  cut  the  head  at  such  an  angle  to  the  face  that  even 
if  the  stone  be  set  with  a  batter  the  face  will  still  slope  toward  the 
outer  edge. 

With  stone  that  does  not  break  squarely,  as  much  trouble  comes 
from  the  joints,  perhaps,  as  from  any  other  source.  Hudson  Eiver 
stone  spalls  off  under  the  hammer  and  often  leaves  large  re-entrant 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC.  465 

holes  at  the  end,  so  that  the  curb  when  set,  although  coming  close 
together  at  the  top,  a  few  inches  down  shows  a  wide  joint.  While 
no  requirements  should  be  made  that  will  unduly  increase  the 
cost  of  the  work,  such  joints  should  not  be  allowed.  If  the  curb 
be  set  in  concrete,  the  joints  should  be  made  tight,  as  far  down  at 
least  as  the  concrete,  although  it  is  not  necessary  to  have  them  full 
to  the  entire  depth  of  the  stone. 

Radius  of  Curb  at  Corners. — Engineers  vary  greatly  in  their 
practice  as  to  the  radii  used  at  curb-corners.  Curved  stone  costs 
more  per  foot  than  straight.  Consequently  the  less  amount  of 
curved  work  required,  the  cheaper  it  will  be  obtained.  The  mini- 
mum radius  that  has  been  used  is  2  feet,  and  this  could  be  ob- 
tained in  one  stone,  so  that  the  total  length  of  curved  curb  at  the 
right-angled  corner  was  practically  3  feet.  This  is  an  extreme 
case  and  should  only  be  used  where  the  cost  of  curved  stone  is  ex- 
treme and  the  appropriation  for  the  work  small.  By  increasing 
the  radius  to  4  feet  the  corners  can  be  gotten  out  in  two  stones  of 
the  same  length  and  can  be  cut  fro«i  much  smaller  stones. 

The  general  practice  is  to  make  the  radius  from  6  to  12  feet. 
Too  large  a  radius  requires  a  great  amount  of  curved  stone  to  be 
used,  and  the  curbing  when  set,  although  making  a  good  appear- 
ance and  being  easy  for  vehicular  travel,  is  inconvenient  for  pedes- 
trians on  the  sidewalk,  as,  if  two  or  more  persons  be  walking 
abreast,  the  one  nearest  the  roadway  reaches  the  curb  considerably 
sooner  than  the  one  on  the  other  side  and  awkwardness  ensues. 
In  Brooklyn,  X.  Y.,  a  radius  of  6  feet  was  used  for  a  considerable 
time  and  gradually  increased  to  12  feet.  This,  however,  was  con- 
sidered excessive,  and  in  1898  the  following  requirement  was 
adopted  in  the  Department  of  Highways  of  Brooklyn,  New  York: 

"  On  all  street-corners  where  angles  between  intersecting  curbs 
are  more  than  80°  and  less  than  100°  the  corners  having  a  radius 
of  9  feet  shall  be  used,  and  where  the  interior  angle  formed  of  in- 
tersecting curbs  is  less  than  80°  the  curbs  having  a  radius  of  12 
feet  shall  be  used,  and  when  the  interior  angle  is  greater  than  100° 
a  radius  of  6  feet  shall  be  used." 

Specifications  for  curbing  in  different  cities  do  not,  as  a  rule, 
specify  what  radius  will  be  required,  but  provide  that  the  curbs 


466        STREET  PAVEMENTS  AND  PAVING   MATERIALS. 

shall  be  set  at  all  corners  cut  to  such  a  radius  as  the  City  Engineer 
may  require. 

Foundation. — The  early  practice,  and  in  fact  down  to  within, 
comparatively  few  years,  was  to  set  the  curb  either  upon  the  natural 
soil  of  the  street  or  a  foundation  of  sand  or  gravel.  This  artificial 
foundation  was  necessary  in  order  to  have  the  stone  firmly  bedded, 
and  also  to  provide  drainage.  In  naturally  sandy  soils  this  moisture 
provision  is  not  required.  Some  engineers,  where  the  earth  is 
clayey,  lay  drain-tiles  under  the  curb  and  connect  them  with  a 
catch-basin  in  order  to  drain  the  soil  and  prevent  its  heaving  and 
displacing  the  curb  by  the  action  of  the  frost. 

At  the  present  time,  when  improved  pavements  with  concrete 
base  have  come  into  such  general  use,  it  has  been  found  more  sat- 
isfactory to  set  the  curbing  in  concrete.  This  allows  the  curb  to 
be  set  in  place  with  the  knowledge  that  it  will  be  maintained  in  this 
position  permanently,  and  insures  a  good  pleasing  appearance  and 
also  a  more  durable  curb,  as,  if  kept  in  position,  it  will  be  subject 
to  very  much  less  wear  than  it  otherwise  would.  Figures  51  and 


52  show  curbs  of  different  depth  as  set  in  concrete.  The  extra 
amount  of  concrete  required,  as  shown  in  these  figures,  is  practi- 
cally 1  cubic  foot  for  a  15-inch  curb,  and  1J  cubic  feet  for  a  curb 
20  inches  in  depth.  In  setting  a  curb,  some  engineers  require  also 
that  the  stone  should  be  kept  apart  at  the  end  by  the  insertion  of 
a  metal  shim  or  piece  of  hoop-irom.  The  object  of  this  is  to  prevent 
the  spalling  off  the  end  of  the  curbs  if  they  should  settle.  This, 
however,  seems  to  be  a  useless  requirement,  as  observation  of  a 
great  many  miles  of  curbing,  set  stone  to  stone,  has  shown  but  a 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC. 


467 


Arery  small  percentage  of  any  joints  injured  in  this  way.  This  is 
for  a  curb  set  on  sand,  and  when  used  with  a  concrete  base  the 
•danger  of  any  settlement  is  reduced  to  a  minimum,  and  it  is  safe 
to  require  in  all  cases  that  the  curb  be  set  stone  to  stone  at  the 


Limestone.  —  In  some  localities  limestone  has  been  used  for  curb- 
ing. This  material,  however,  is  not  very  well  adapted  for  this  work. 
It  is  liable  to  be  too  soft  and  is  subject  in  many  cases  to  the  action 
of  the  water.  If  circumstances  are  such  that  limestone  must  be 


FIG.  52. 

used  for  economical  reasons,  care  should  be  taken  to  get  the  best 
that  is  available.  Some  limestones  are  as  durable,  as  far  as  the 
action  of  the  weather  is  concerned,  as  perhaps  almost  any  other 
stone,  but  all  are  not.  Some  curbing  made  of  limestone  in  Omaha, 
Neb.,  disintegrated,  and  as  curbing  had  practically  disappeared  in 
about  six  years  after  it  was  set.  Fortunately  but  little  of  this  par- 
ticular kind  was  used. 


Specifications  for  Curbing. 

The  following  specifications  for  curbing  of  different  materials, 
in  different  cities,  give  a  good  idea  of  the  requirements  of  the  best 
practice: 

Liverpool,  Eng.     First-class  Specifications. 

"  Curbstones  to  be  of  syenite,  straight  or  circular  as  required, 
•6  inches  thick  at  top,  7  inches  thick  at  5  inches  below,  and  not  less 
than  that  thickness  for  the  remainder  of  the  depth.  To  be  not  less 


468        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

than  12  inches  deep  nor  less  than  3  feet  in  length;  to  be  carefully 
dressed  on  top,  8  inches  down  face  and  3  inches  down  back,  the 
remainder  of  each  stone  to  be  hammer-dressed.  The  head  joints 
to  be  neatly  and  accurately  squared  throughout  the  entire  depth." 

Cincinnati,  0. 

"  Curbs  to  be  not  less  than  5  feet  long,  except  where  it  is  neces- 
sary to  cut  the  stone  to  fit  circular  corners,  21  inches  deep  and  5 
inches  thick,  bases  to  be  equal  to  their  top,  the  stone  to  be  squared 
and  hammer-dressed,  to  a  width  of  5  indies,  the  top  to  a  depth  of 
10  inches  on  each  end,  12  inches  on  the  face  next  to  the  gutter,  and 
3  inches  on  the  back.  The  end  joints  of  the  hammer-dressed  stone 
is  not  to  exceed  £  inch  for  10  inches  down  from  the  top  and  \  inch 
for  the  remaining  11  inches  to  the  bottom  of  the  stone." 

St.  Louis,  No. 

"  All  curbstones  shall  be  of  the  best  quality  of  granite.  The 
curb  shall  have  a  straight  face,  fine  pean-hammer-finish  on  the 
side  toward  the  roadway  for  the  full  depth  of  the  stone,  and 
pitched  to  line  and  rough-pointed  on  the  side  toward  the  side- 
walk to  a  depth  of  6  inches  from  top  of  curb,  and  shall  have  close- 
under- joints  to  the  full  depth  of  the  stone,  and  no  stone  shall  be 
less  than  4£  feet  long,  nor  less  than  6  inches  thick,  nor  less  than 
16  inches  deep.  The  curb  shall  be  set  on  concrete  6  inches  deep 
and  12  inches  wide,  backed  with  concrete  6  inches  wide  and  10 
inches  deep  to  6  inches  below  the  top  of  curb." 

New  York. 

"  New  curbstones  shall  be  hard,  sound,  fine-grained,  and  uni- 
form-colored bluestone,  shall  be  free  from  seams  and  other  imper- 
fections, and  shall  be  equal  in  quality  to  the  best  North  River 
bluestone. 

"  They  shall  be  inches  in  depth,  from  three  and  one-half 

to  eight  feet  in  length,  and  not  less  than  five  inches  in  thickness, 
(except  as  noted  for  bottom  of  curb)  with  square  ends  of  the  full 
average  width. 

"  The  face  for  a  depth  of  inches  and  the  top,  on  a  bevel 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC.  469 

of  one-half  an  inch  in  its  matched  width  of  five  inches,  shall  be 
dressed  to  true  planes  and  free  from  depressions,,  equal  to  '  four- 
cut  '  axe-work.  The  face  dressing  of  curbstones  set  adjacent  to 
gutters  exceeding  the  depth  above  specified  shall  be  correspond- 
ingly extended  by  the  Contractor  without  extra  charge  therefor. 

"  The  remainder  of  the  face,  and  the  back  to  a  depth  of  four 
inches  from  the  top,  shall  be  out  of  wind  and  shall  be  pointed  to 
a  fair  surface  free  from  irregularities  greater  than  one-quarter  of 
an  inch,  measured  from  a  straight-edge. 

"  All  edges  bordering  dressed  surfaces  shall  be  sharply  and 
truly  defined,  and  the  bottom  of  the  curb  shall  be  rough-squared 
with  a  width  not  less  than  three  inches  at  any  point. 

"  For  the  full  width  of  the  stone  for  a  distance  down  of  six 
inches  from  the  top  and  therebelow  to  the  bottom  for  a  width  of 
two  inches  back  from  the  face,  the  ends  shall  be  squarely  and 
evenly  jointed  with  no  depression  greater  than  one-quarter  of  an 
inch  measured  from  a  straight-edge,  and  in  such  jointing  care 
must  be  taken  to  .preserve  the  square  ends  of  the  curbstones  as 
furnished,  and  the  edges  as  aforesaid." 

Rochester,  N.  Y. 

"  The  new  curbstone  must  be  of  the  best  quality  of  hard 
Medina  sandstone  of  uniform  color.  The  stone,  including  those 
in  curves,  shall  be  not  less  than  3  feet  in  length,  6  inches  thick, 
18  inches  deep,  and  matched  width  throughout.  Top  and  arris 
shall  be  axed  to  a  smooth  surface  with  a  bevel  on  top  of  J  inch, 
unless  otherwise  directed.  Face  of  curb  shall  be  dressed  to  a  true 
surface,  which  shall  in  no  place  vary  more  than  J  inch  from  a  true 
plane  for  10  inches  down  from  the  top.  The  back  shall  be  point- 
dressed  for  3  inches  down  and  hammer-dressed  on  the  remainder 
of  the  surface.  The  back  shall  be  roughed  off  parallel  to  the  top 
and  of  full  width,  not  less  than  6  inches  shorter  than  top.  The 
face  shall  be  parallel  and  true  to  the  line  and  curve  to  which  it 
is  laid.  The  ends  for  at  least  12  inches  down  from  the  top  shall 
be  truly  squared  and  dressed,  so  that  when  laid  the  end  joints  for 
the  depth  of  12  inches  and  full  width  of  the  stone  shall  not  ex- 
ceed inch." 


470        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Rochester  sets  its  curb  on  concrete  and  lays  a  3-inch  drain-tile 
under  the  concrete  foundation. 


Concrete  Curb. 

In  some  sections  of  the  country  where  stone  of  any  kind  is  not 
available,  curbing  has  been  made  artificially  of  Portland-cement 
concrete.  This  makes,  when  honestly  laid,  a  substantial  and 
pleasing  curb.  With  the  great  increase  of  the  manufacture  of 
Portland  cement  in  this  country  this  material  can  be  had  cheaply 
in  nearly  all  sections,  so  that  the  artificial  curb  can  compete  suc- 
cessfully in  price  with  the  natural  stone.  It  has  been  laid  to  a 
considerable  extent  in  the  West,  and  its  use  is  being  rapidly  ex- 
tended to  eastern  cities.  While  perhaps  it  will  not  stand  the 
hammer  and  shock  of  heavy  traffic  as  well  as  natural  stone,  it  will 
give  gox)d  satisfaction  on  residence  streets.  To  obviate,  however, 
as  much  as  possible  the  damage  liable  to  be  caused  by  trucks,  the 
corner  of  the  curb  has  been  protected  in  some  instances  by  a  steel 
rail  as  shown  in  Fig.  53.  It  makes  a  useful  addition  to  the  curb. 


T 
I 
I 

I 

18' 


FIG.  53. 


An  additional  price  of  25  cents  per  lineal  foot  was  charged  for 
this  steel  corner  on  curbwork  in  Brooklyn  in  1899.  Considering 
the  weight  of  the  steel  and  extra  labor  of  using  it,  this  cost  seems 
very  excessive  and  should  be  reduced  during  the  coming  years. 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC.  471 


Concrete  Gutter. 

Gutters  of  cement  concrete  are  often  used  in  conection  with 
this  curb  on  asphalt  and  macadam  streets.  Some  contractors  pre- 
fer to  build  the  two  combined  in  one  piece,  while  others  build 
the  curb  first  and,  before  the  concrete  is  entirely  set,  construct  the 
gutter,  making  only  a  partial  bond  with  the  curb,  so  that  any 
heaving  on  account  of  frost  will  be  taken  up  by  the  joints,  where 
otherwise  it  might  break  the  body  of  the  concrete. 

Where  this  gutter  is  used  for  macadam,  and  the  subgrade  of 
the  street  is  soft,  precaution  must  be  taken  to  prevent  the  gutter 
from  being  lifted  up  out  of  position  by  the  roller  being  used 
•close  to  the  edge  of  the  gutter.  In  one  or  two  instances  the  gutter 
was  badly  cracked  and  lifted  in  this  way  on  several  Brooklyn 
streets.  This  trouble  was  obviated  by  laying  a  plank  9  inches  deep 
next  to  the  edge  of  the  gutter  and  extending  6  inches  below  it, 
thus  preventing  the  earth  from  being  forced  under  the  gutter  and 
lifting  it.  Specifications  for  this  curb  and  gutter  on  Ocean  Ave- 
nue were  as  follows: 

"  Curb  and  gutter  shall  be  made  in  lengths  not  exceeding 
twenty  feet  with  joints  for  the  full  depth  of  curb  and  gutter.  The 
concrete,  except  for  one  inch  immediately  next  to  the  top  surface 
of  face  of  the  curb  and  gutter,  shall  be  made  of  one  part  of  the 
best  quality  of  Portland  cement,  two  parts  pure,  clean,  sharp  sand, 
and  four  parts  clean  broken  stone.  The  sand  shall  be  carefully 
screened  and  free  from  loam  or  other  foreign  material.  The  stone 
used  shall  be  broken  trap-rock  or  granite  varying  in  size,  none 
of  which  shall  be  more  than  one  and  one-half  inches  nor  less  than 
one-half  inch  in  any  direction,  and  it  must  be  free  from  dust  or 
flirt.  The  second  or  finishing  course  covering  the  top  surface  and 
face  of  curb  of  a  thickness  of  not  less  than  one  inch  shall  be  com- 
posed of  one  part  of  the  best  quality  of  Portland  cement  and  one 
and  one-half  parts  of  finely  crushed  granite.  This  crushed  stone 
shall  be  approximately  cubical  in  shape,  all  perfectly  fresh  and 
clean,  and  of  sizes  from  one-quarter  inch  downward,  and  must  be 
free  from  dust.  The  cement  and  crushed  stone  shall  be  mixed 
dry,  after  which  water  shall  be  added  and  mortar  worked  into  a 


472        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

thick  uniform  paste,  which  shall  be  laid  on  the  first  layer  and 
trowelled  and  rubbed  to  a  hard,  smooth,  uniform  surface.  The 
color  of  the  concrete  must  be  uniform  in  all  cases  and  must  be  as- 
nearly  as  possible  the  color  of  selected  Hudson  River  bluestone,, 
or  similar  in  color  to  the  sample  of  concrete  in  the  Engineer's 
office." 

Assuming  a  barrel  of  cement  to  contain  4  cubic  feet  of  loose 
material  according  to  experiments  made  in  the  laboratory  of  the 
Department  of  Highways  in  Brooklyn,  referred  to  on  page  123,. 
it  will  require  1.7  barrels  of  cement,  0.5  cubic  yard  of  sand,  and 
1  cubic  yard  of  broken  stone  to  make  1  cubic  yard  of  concrete  for 
the  curb;  and  1  barrel  of  cement  and  6  cubic  feet  of  crushed  stone 
will  make  about  6  cubic  feet  of  mortar. 

Assuming  the  cost  of  Portland  cement  at  $2.25  per  barrel,, 
sand  at  $1  per  cubic  yard,  crushed  stone  at  $2.25  per  cubic  yard,, 
broken  stone  at  $2.25  per  cubic  yard,  the  cost  of  one  cubic  yard 
of  concrete  and  mortar  will  be  as  follows: 

CONCRETE. 

1  7-10  bbls.  cement  at  $2.25 $3.83 

1/2  cubic  yard  of  sand  at  $1 .50 

1  cubic  yard  of  stone  at  $2.25 2.25 

Total  per  cubic  yard  for  material $6.58 

Or  25  cents  per  cubic  foot. 

MORTAR. 

4y2  bbls.  cement  at  $2.25.. $10.12 

1  cubic  yard  crushed  stone  at  $2.25 2.25 


Total  per  cubic  yard  for  material 12.37 

Or  46  cents  per  cubic  foot. 

The  quantity  of  material  required  to  lay  200  lineal  feet  of 
curb  is: 

15  cubic  feet  of  mortar  at  46  cents $6.90 

161  cubic  feet  of  concrete  at  25  cents 40.25 


Total $47.15 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC.  473 

And  for  200  lineal  feet  of  gutter  there  will  be  required: 

33  cubic  feet  of  mortar  at  46  cents $15.18 

167  cubic  feet  of  concrete  at  25  cents 41.75 


Total $56.93 

To  lay  200  lineal  feet  of  curb  in  one  day  it  will  take 

1   carpenter $3.00 

1  helper 1.50 

1  mason 3.50 

8  helpers  at  $1.50 12.00 


Total  for  labor $20.00 

Making  the  entire  cost  of  200  lineal  feet  of  curb  $67.15,  or  34 
cents  per  lineal  foot.  The  carpenter  and  helper  will  be  engaged 
in  setting  up  and  repairing  the  forms  necessary  for  keeping  the 
concrete  in  place,  and  to  the  above  34  cents  should  be  added  a 
small  sum  to  pay  for  the  lumber,  the  exact  amount  to  be  deter- 
mined by  the  quantity  of  work,  but  it  will  be  very  small.  No  ex- 
cavation is  included  in  the  above  estimate. 

To  lay  200  lineal  feet  of  gutter  per  day,  constructed  2  feet  wide 
and  6  inches  thick,  will  take: 


6  helpers  at  $1.50 9.00 


Total $12.50 

Which  added  to  the  cost  of  material  for  gutter  makes  the  total 
cost  for  200  lineal  feet  of  gutter  $69.43,  or  35  cents  per  lineal  foot, 
making  the  total  cost  of  the  combined  curb  and  gutter  69  cents  per 
lineal  foot. 

These  figures  are  given,  not  with  the  expectation  that  they 
will  be  exact  for  every  locality,  but  to  show  the  amount  of  mate- 
rial and  labor  required  for  a  certain  amount  of  construction.  Any 
change  necessary  from  the  differences  in  the  cost  of  labor  or 
material  from  that  given  in  the  estimate  can  readily  be  made,  but 
the  quantities  can  be  taken  as  correct. 

The  cost  of  stone  curb  varies  greatly  with  localities  and  kinds 
of  material.  It  has  already  been  given  for  granite  at  Albany.  In 


474        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Brooklyn,  K  Y.,  the  average  price  for  bluestone,  according  to  the 
specifications  previously  given,  is  from  75  to  80  cents  per  lineal 
foot.  In  other  cities  nearer  quarries  the  prices  are  very  much 
lower,  so  that  the  range  can  be  safely  said  to  be  from  40  cents  to 
$1  per  lineal  foot,  according  to  location,  material,  and  dimensions 
of  the  curb. 

Sidewalks. 

In  the  business  and  solidly  built  up  residence  portions  of  a 
city  the  sidewalks  generally  extend  from  the  curb-line  to  the  court- 
yard or  property-line.  When  in  a  business  section,  as  often  hap- 
pens, the  area  wall  is  built  on  the  curb-line,  the  sidewalk  is  often 
made  of  a  thickness  strong  enough  to  resist  any  transverse  strain 
which  it  is  liable  to  be  subjected  to,  and  often  extends  from  the 
building-line  to  and  resting  upon  the  area  wall,  where  it  is  made 
thick  enough  to  act  as  a  curb.  This  is  technically  termed  "  plat- 
form walk."  In  such  cases  the  flags  are  often  supported  by  double 
angle-irons  running  from  the  building  to  the  area  wall.  The  joints 
should  be  poured  and  calked  with  lead  to  prevent  water  from  the 
;i  treet  running  into  the  area.  Coal-holes  are  often  cut  through 
these  walks,  when  a  channel  should  be  cut  around  on  the  upper 
side  so  that  the  surface-  water  will  be  drained  from  the  hole  to  the 
gutter. 

In  suburban  localities  it  is  not  necessary  nor  desirable  that  the 
walks  should  extend  from  the  curb  to  the  building-line.  A  walk 
5  feet  in  width  will  allow  two  people  to  walk  abreast  comfortably, 
and  one  of  8  feet  will  permit  passing;  so  that  it  would  seem  that  a 
width  of  8  feet  would  be  sufficient  for  any  suburban  street,  and 
that  5  feet  should  be  adopted  as  the  minimum. 

Slope  of  Walk. — All  walks  must  follow  naturally  the  grade  of 
the  street.  They  all  should  be  laid,  too,  with  a  slope  from  the 
property-line  towards  the  curb,  to  allow  water  falling  upon  it  to 
flow  freely  towards  the  gutter.  Some  little  variation  as  to  the 
amount  of  this  slope  exists  in  different  cities.  A  fall  of  |  inch  to 
the  foot  will  be  equal  to  a  grade  of  2  per  cent.  This  will  allow 
irater  to  flow  f-reely  on  the  smooth  surface,  and  will  not  be  suffi- 
ciently steep  to  cause  trouble  from  slipperiness. 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC.  475 

The  location  of  the  sidewalk  has  previously  been  discussed. 

Material. — The  materials  of  which  sidewalks  have  been  con- 
structed 'are  wood,  gravel,  coal-tar,  stone  of  different  kinds,  brick, 
and  cement.  The  last  three,  however,  are  the  only  ones  that  are. 
used  to  any  great  extent  in  cities  for  permanent  walk.  The  con- 
struction of  walks  of  wood  and  gravel  is  simple  and  need  not  be  re- 
ferred to.  Coal-tar  walks  (or  concrete,  as  they  are  often  called) 
has  been  used  to  considerable  extent  in  villages  and  smaller  towns. 
Its  use  is  subject  to  the  same  objections  as  that  of  the  coal-tar 
pavement.  It  has,  however,  been  very  successfully  used  in  small 
cities  and  villages. 

In  some  cities  of  Europe,  Paris  especially,  sidewalks  have  been 
laid  with  asphalt  mastic.  This  is  somewhat  similar  to  the  asphalt 
used  in  the  pavement,  but  is  much  softer  and  is  applied  to  the 
concrete  base  with  a  trowel  in  a  manner  very  similar  to  cement 
mortar.  The  specifications  require  that  the  mastic  shall  contain 
not  less  than  15  nor  more  than  18  per  cent  of  bitumen,  and  the 
sidewalk  material  must  contain,  bv  weight,  bitumen-mastic  100 
parts,  bitumen  for  fluxing  6  parts,  sand  60  parts.  This  material, 
however,  has  never  been  used  to  any  great  extent  in  this  country. 

Stone  Sidewalks. 

The  exact  character  of  the  stone  to  be  used  in  any  locality  will 
be  determined  to  a  great  extent  by  its  availability.  Where  very 
heavy  stones*  are  required  granite  is  generally  used,  but  it  is  ex- 
pensive and  wears  smooth  and  slippery  under  traffic,  so  that,  where 
laid  on  crowded  business  streets,  it  often  has  to  be  picked  up  and 
roughened  to  prevent  its  becoming  too  slippery.  It  has  been  used 
quite  freely  in  business  sections  in  Boston,  New  York,  and  other 
large  cities  where  water-transportation  can  be  had,  but  in  New  York 
almost  all  of  the  natural-stone  sidewalks  are  laid  with  Hudson 
River  bluestone. 

Sizes  of  Stone. — The  size  of  the  individual  stones  laid  in  the 
walk  should  be  determined  principally  by  economical  reasons.  The 
larger  the  stones  tftiat  can  be  used  the  better,  as  there  will  be  fewer 
joints  and  less  liability  of  the  stones  to  be  come  uneven;  but  if 
the  size  be  made  too  great,  the  cost  will  be  excessive.  It  is  more 


476        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

expensive  per  square  foot  to  quarry  and  transport  large  stones  than 
small.  There  is  also  more  liability  of  loss  from  breakages,  so  that 
care  should  be  taken  not  to  specify  «a  size  that  will  cause  too  great 
a  cost. 

If  the  minimum  width  of  5  feet  be  used,  the  stone  should  ex- 
tend the  entire  width  of  the  walk,  and  should  contain  at  least  15 
square  feet,  and  it  would  perhaps  be  as  satisfactory  a  plan  as  any 
to  specify  that  no  stone  s'hould  contain  less  than  a  given  number 
of  square  feet,  according  to  the  capabilities  of  the  quarry  from 
which  the  stone  is  to  be  obtained.  It  is  sometimes  desired,  however, 
for  other  reasons  than  that  of  economy  to  cut  the  stone  into  smaller 
and  regular  pieces,  often  18  or  20  inches  square.  This  would  be 
more  expensive  than  in  the  larger  sizes,  but  is  adopted  for  appear- 
ance' sake.  The  stones  in  such  cases  should  be  set  on  a  solid 
foundation  and  in  the  manner  as  shown  in  Fig.  54. 


FIG.  54. 

The  thickness  of  the  stone  when  laid  on  a  sand  base  depends 
somewhat  upon  the  character  of  the  material,  but  for  residence 
purposes  3  inches  will  perhaps  be  sufficiently  thick.  In  business 
sections,  however,  where  the  walks  will  be  subjected  to  having 
heavy  articles  dumped  upon  them  from  trucks,  a  greater  thickness 
will  be  necessary. 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC. 


4-77 


Foundation. — This  will  depend  somewhat  upon  the  character  of 
the  soil,  but  ordinarily  6  inches  of  sand  or  steam-cinders  will  be 
sufficient  for  stone  nagging. 

Sandstones  as  a  rule  make  the  most  satisfactory  sidewalks. 
They  are  sufficiently  hard  to  withstand  wear  satisfactorily,  and 
their  gritty  nature  prevents  them  from  wearing  smooth  and  slip- 
pery. Limestone,  however,  has  been  used  with  good  success,  espe- 
cially that  which  comes  from  the  quarries  near  Bedford,  Ind. 


Artificial  Walks. 

In  sections  of  the  country  where  stone  is  not  available  artificial 
material  can  generally  be  used  to  best  advantage,  and  recourse  is 
then  had  to  brick  and  Portland  cement. 

Brick. — Brick  has  been  used  as  a  material  for  sidewalks  for 
many  years.  The  cities  of  Philadelphia  and  Boston  probably  have 
laid  more  brick  walks  than  any  others.  The  bricks  are  arranged  in 
many  ways,  as  shown  in  Figs.  55,  56,  and  57,  according  to  individual 


... 

FIG.  55. 


FIG.  56. 


FIG.  57. 


taste.  They  are  generally  of  the  ordinary  building-brick  size,  but 
burned  especially  hard.  They  should  be  of  an  equal  degree  of 
hardness,  so  that  all  should  wear  evenly  and  prevent  the  surface 
from  being  rough.  They  should  also  be  of  uniform  size  and  shape. 
As  a  rule,  bricks  are  laid  flatwise,  but  sometimes,  where  an  espe- 
cially solid  walk  is  desired,  they  are  laid  on  edge  with  cemented 
joints.  The  foundation  is  generally  of  sand,  and  the  joints  also 


478        STREET  PAVEMENTS  AND  PAYING  MATERIALS. 

filled  with  sand.  Special  blocks  are  sometimes  made  of  clay  and 
burned  for  sidewalk  purposes.  When  large  these  are  often  corru- 
gated on  top,  so  as  not  to  be  slippery.  This  plan  has  not  been  used 
to  any  great  extent,  as  any  broken  or  unfit  material  is  almost  a  total 
loss,  as  it  cannot  be  used  to  advantage  in  any  other  construction. 

Cement  Walks. — Within  the  past  few  years  sidewalks  made  of 
Portland  cement  have  come  into  use  very  largely,  both  in  the 
larger  eastern  cities  and  those  smaller  ones  of  the  West  where  stone 
cannot  be  'had  except  at  considerable  expense.  The  walks  are 
smooth,  of  pleasant  appearance,  and,  when  well  constructed,  dur- 
able. They  must,  however,  like  all  construction  of  cement,  be 
honestly  and  thoroughly  built.  Most  of  the  failures  of  cement  side- 
walks are  caused  by  the  use  of  improper  or  too  little  cement,  or  on 
account  of  the  work  being  performed  by  dishonest  contractors^ 
Cement  walks  are  generally  laid  continuously,  except  that  joints  are 
made  at  frequent  intervals  to  allow  for  expansion,  so  that  any 
cracking  which  may  be  caused  will  be  regular  and  at  places  pre- 
pared for  it.  In  ordinary  climates  where  the  variation  in  tempera- 
ture from  summer  to  winter  is  not  too  great,  lengths  of  5  feet  can 
be  safely  used  without  any  danger  of  irregular  cracking. 

Small  pieces  of  cement  tiling  are  sometimes  made  and  allowed 
to  thoroughly  set  and  harden  before  being  laid  in  the  walk.  In  such 
cases  a  foundation  of  concrete  is  prepared  and  then  the  tiles  are 
laid  upon  the  base  and  set  in  Portland-cement  mortar.  These  tiles, 
are  made  square,  hexagonal,  or  octagonal  in  shape,  and  colored  to 
suit  the  individual  fancy.  At  the  present  time  they  are  not  used 
to  any  great  extent,  as  most  of  the  cement  walks  are  laid  practically 
in  one  sheet  except  as  above  described. 

Specifications  for  such  walk  in  Brooklyn  provided  for  the  con- 
crete to  be  made  as  heretofore  specified  for  concrete  curb,  and  to  be 
laid  on  7  inches  of  clean  steam-cinders  which  had  been  thoroughly 
rolled  and  tamped  until  they  were  solid  and  compact.-  The  walk 
was  laid  in  blocks  4  feet  square,  the  joints  being  placed  opposite 
the  joints  of  the  curb.  In  laying  this  walk  after  the  concrete  was 
in  place,  it  was  cut  up  into  blocks  4  feet  square  by  irons  especially 
prepared  for  that  purpose.  Besides  the  base  the  walk  consisted  of 
4  inches  of  concrete  and  1  inch  of  mortar.  The  labor  organization 
was  as  follows: 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC.  479 

6  masons  at  $3.50 $21.00 

6  men  tamping,  at  $1.50 9.00 

14  men  making  concrete,  at  $1.50 21.00 

3  men  mixing  surface  mortar,  at  $1.50 4.50 

4  men  carrying  surface  mixture,  at  $1.50 6.00 

4  laborers  grading,  providing  water,  etc.,  at  $1.50 6.00 

1  foreman. . .               3.00 


Total  for  labor $70.50 

• 

This  gang  laid  2560  square  feet  of  walk  per  day.  The  concrete- 
n^ixers  also  wheeled  the  concrete  from  the  mixing-boards  to  the 
work.  This  amount  of  walk  required  the  following  amount  of 
materials: 

8  cubic  yards  of  mortar,  at  $12.37. $98.96 

32  cubic  yards  of  concrete,  at  $6.58 210.56 

71  cubic  yards  cinders,  at  50  cts 35.50 

Total  for  material 345.02 

Labor 70.50 

$415.52 

Or  per  square  foot  16 J  cents. 

The  Philadelphia  specifications  for  cement  sidewalks  require 
that  the  excavation  shall  be  made  8  inches  below  the  finished 
grade  of  the  sidewalk.  Upon  this  subbase  shall  be  placed,  and 
thoroughly  rammed,  3  inches  of  gravel  screenings,  broken  brick,, 
broken  stone  or  cinders.  Upon  this  foundation  shall  be  laid  3- 
inches  of  cement  concrete  made  of  one  part  of  Portland  cement 
and  two  parts  of  sand  and  broken  stone  of  such  size  as  will  pass 
through  a  l^-inch  ring,  and  in  such  quantity  that  when  solidly 
rammed  and  compacted  free  mortar  shall  appear  upon  the  surface. 
Upon  the  concrete  foundation  shall  be  laid  the  wearing  surface. 
This  is  2  inches  in  thickness  and  composed  of  one  part  of  imported 
Portland  cement  and  two  parts  of  crushed  granite,  free  from  dust,, 
the  largest  particles  of  which  will  pass  through  a  J-inch  sieve. 

The  following  is  extracted  from  the  specifications  of  New  York 
City  relating  to  the  construction  of  bluestone  sidewalks: 

"All  new  flagging  shall  be  of  bluestone  of  satisfactory  and 
uniform  color  and  equal  in  quality  to  the  best  North  River  blue- 


480        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

stone,  and  shall  be  free  from  sap,  seams,  flaws,  drill-holes,  and  dis- 
colorations.  It  shall  have  a  smooth  surface,  be  out  of  wind,  and 
not  less  than  three  inches  thick  at  any  point,  and  shall  be  five 
feet  in  length  and  not  less  than  three  feet  in  width,  except  that 
wherever  in  sidewalks  an  old  stone  of  superior  dimensions  is 
broken,  but  one  new  stone  shall  be  put,  which  must  be  in  length 
and  width  not  les,s  than  the  old  stone.  New  flagstone  of  smaller 
size  shall  be  furnished  when  directed  by  the  Engineer,  such  stone 
to  be  of  specification  thickness  and  be  used  when  necessary  to 
match  existing  courses  on  walks  already  partly  flagged,  and  in  the, 
closure  course  of  such  walks  as  are  to  be  flagged  for  the  full  width. 

"  All  stone  shall  be  chisel-dressed  with  opposite  sides  parallel 
•and  adjacent  sides  at  right  angles,  on  the  four  edges  a  distance 
down  of  one  inch  from  the  top  and  at  right  angles  thereto,  and 
such  dressing  shall  be  entirely  completed  before  said  stone  shall 
be  placed  on  the  bed  prepared. 

"  Flagging  shall  be  laid,  so  far  as  is  practicable,  in  regular 
courses  five  feet  in  width,  and  shall  be  firmly  and  evenly  bedded 
to  the  grade  and  pitch  required  on  four  inches  of  steam-ashes, 
clean,  gritty  earth  or  sand,  free  from  clay  or  loam;  the  work  to 
be  brought  to  an  even  surface,  with  all  joints  close  and  thoroughly 
filled  for  their  full  depth  with  cement  mortar  composed  of  equal 
parts  of  the  best  quality  of  American  Portland  cement  and  clean, 
sharp  sand,  and  left  clean  on  the  surface;  but  no  more  mortar 
shall  be  mixed  at  any  one  time  than  can  be  used  'within  one-half 
an  hour,  nor  shall  any  mortar  be  laid  against  any  edge  of  a  stone 
until  the  stone  to  abut  thercagainst  shall  have  been  completely 
•dressed  ready  for  laying.'' 

Gutters. 

It  often  happens  that  a  street  is  improved  by  grading,  curbing, 
and  guttering,  without  the  laying  of  any  pavement.  In  such  cases 
the  gutter  is  generally  formed  of  the  same  shape  as  it  would  have 
been  if  the  street  was  entirely  paved,  and  of  granite,  Belgian 
block,  vitrified  brick,  or  cobblestone,  as  the  case  might  require. 
Whatever  material  is  used,  it  should  be  laid  in  the  same  manner 
and  according  to  the  same  specifications  as  a  stone  pavement  upon 
the  same  foundation. 


WIDTH  OF  STREETS  AND  ROADWAYS,  ETC. 


481 


Special  gutters  are  also  constructed  for  streets  that  are  mac- 
adamized. These  are  of  the  same  material  as  those  just  men- 
tioned, and  should  be  constructed  in  the  same  way.  It  sometimes 
happens,  however,  that  a  street  is  macadamized  in  the  suburbs 
when  it  is  not  desired  to  go  to  the  expense  of  setting  a  regular 
curbstone.  In  this  event  the  gutter  is  built  in  the  form  shown  in 


U- 


FIG.  58. 


FIG.  59. 


Pig.  58,  the  shoulder  taking  the  place  of  a  curb.    Fig.  59  shows 
the  form  of  cement  gutter  without  curb  as  used  in  St.  Louis. 


Grades. 

The  gradient  of  paved  streets  is  very  important.  The  maxi- 
mum varies  greatly  in  different  cities  according  to  the  local 
topography.  In  cities  like  Chicago  the  problem  is  to  obtain  suffi- 
cient grade  for  drainage;  while  in  Duluth,  Kansas  City,  and 
Omaha  it  is  difficult  to  get  a  passable  grade  on  many  streets  with- 
out excessive  cuts  and  embankments.  In  the  latter  city  one  street 
was  graded  where  a  cut  of  sixty  feet  was  made  with  fills  even 
greater.  Before  the  time  of  cable  and  electric  street-cars  a  grade 
of  5  or  6  per  cent  was  considered  the  limit  for  street-car  streets, 


482        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

but  at  the  present  time  that  element  need  not  be  made  a  ruling- 
factor,  though  a  much  lighter  grade  is  very  desirable. 

No  arbitrary  rule  for  a  maximum  grade  can  be  laid  down.  But 
in  a  city  that  has  been  partially  improved  no  grade  should  be  es- 
tablished in  excess  of  the  maximum  at  that  time  in  force  unless, 
absolutely  necessary. 

New  York  City  has  some  grades  as  steep  as  6  per  cent  on  busi- 
ness streets,  while  in  Brooklyn  there  are  few  in  excess  of  4  per 
cent.  Pittsburg,  Duluth,  Omaha,  and  Kansas  City  are  all  exam- 
ples of  cities  with  excessive  grades  on  paved  streets. 

The  force  required  to  draw  a  load  up  any  grade  can  be  easily: 
ascertained  by  the  following  formula: 

F :  =  Z(iob)  +  T' 

Where  F  =  force,  R  =  rise  in  ICO  feet,  L  =  load,  and  T  — 
force  required  to  draw  L  on  a  level  surface.  This,  however,  is 
theoretical  and  is  based  upon  the  supposition  that  the  incline  is. 
absolutely  regular  and  without  friction. 

When  animal  force  is  used  to  draw  vehicles,  the  problem  is  dif- 
ferent and  the  results  cannot  be  calculated. 

The  -ability  of  a  horse  to  draw  a  load  depends  upon  two  things,, 
his  muscular  force  and  his  foothold  upon  the  pavement.  If  the 
latter  be  such  that  he  can  exert  all  'his  power  without  slipping,  he 
will  be  able  to  use  his  strength  to  the  best  advantage,  and  the 
weight  of  his  load  will  be  limited  by  his  physical  strength.  If,  on 
the  other  hand,  the  surface  of  the  pavement  be  slippery,  so  that 
he  maintains  his  foothold  with  difficulty,  his  available  strength  will 
be  greatly  reduced  and  his  ability  to  stand  up  while  exerting  his. 
strength  will  be  the  controlling  factor.  A  horse,  too,  must  carry 
himself  in  addition  to  his  load,  and  as  the  rate  of  grade  increases,. 
a  certain  amount  of  his  heretofore  available  power  will  be  required 
to  move  himself,  until  finally  a  grade  will  be  reached  which  he  can 
barely  climb  with  no  load  whatever.  This  stage  could  only  be 
arrived  at  by  experiment,  and  would  vary  greatly  with  the  individ- 
ual horse  as  well  as  the  exact  condition  of  each  pavement.  It 
would  be  useless,  then,  to  attempt  to  estimate  in  exact  figures  the 
effect  of  grades  upon  vehicular  travel  when  animal  power  is  used.. 


f 

WIDTH  OF  STREETS  AND  BOADWA7S,  ETC.  483 

It  will  be  safe  to  assume,,  however,  that  a  grade  of  10  per  cent 
be  prohibitive  as  far  as  heavy  trucking  in  concerned. 

In  the  report  of  the  Commission  of  Highways  of  New  York  City 
for  1898  it  is  stated,  quoting  from  a  former  report  of  the  Consult- 
ing Engineer,,  that  established  grades  of  10  per  cent  exist  in  that 
city  upon  a  number  of  streets,  and  instances  of  grades  of  12.17, 
15.17,  and  one  of  18.17  per  cent  are  given.  One  clause  says:  "  But 
the  city  of  New  York  has  apparently  adopted  a  maximum  grade  for 
its  thoroughfares  of  18  per  cent." 

Pittsburg  has  grades  of  17  per  cent,  Duluth  12.2  per  cent,  and 
Kansas  City  16.5  per  cent,  all  on  paved  streets,  while  one  unpaved 
street  in  Pittsburg  has  a  grade  as  steep  as  30  per  cent. 

The  importance  of  constructing  the  best  pavement  for  these 
excessive  grades  can  readily  be  understood.  The  two  principal 
requisites  are  a  smooth,  unyielding  surface  and  foothold  for  horses. 
Asphalt  meets  the  first  requirement,  but  not  the  second.  The  best 
results  will  be  obtained  by  laying  a  block  pavement  of  such  material 
that  it  will  not  wear  smooth  or  waste  away  under  traffic.  It  must 
be  remembered  that  loads  drawn  on  excessive  grades  must  neces- 
sarily be  light  as  compared  to  the  normal  load,  and  that  the  wear 
will  be  due  more  to  the  action  of  the  horses'  feet  than  the  abrasion 
of  the  wheels. 

Hard  sandstone  or  granite  blocks  from  3  to  3£  inches  thick 
with  smooth,  even  heads,  laid  with  open  joints  filled  with  tar  and 
gravel  upon  a  concrete  base,  will  give  satisfactory  results.  Brick 
can  also  be  used.  It  will  not  give  quite  as  good  a  foothold  for 
horses,  but  the  traction  will  be  less.  Either  of  the  above  pavements 
would  last  a  generation  on  most  streets  with  grades  of  more  than 
10  per  cent. 

The  practice  of  making  the  pavement  rough  on  steep  grades 
to  give  horses  a  better  footing  cannot  be  commended,  as  it  increases 
so  much  the  traction  required  to  draw  a  given  load.  A  rough 
stone  pavement  requiring  a  load  to  be  lifted  vertically  over  the 
stones  may  often  cause  the  traction  on  a  nominal  10  per  cent  grade 
to  be  equal  to  the  normal  traction  of  one  of  15  per  cent  or  even 
greater. 

In  establishing  street-grades,  the  points  specified  in  the  ordi- 
nance differ  in  different  cities.  And  in  fact  grades  are  sometimes 


484:        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

fixed  simply  by  referring  to  an  accompanying  profile.  This  prac- 
tice is  very  bad,  as,  if  the  profile  is  lost  or  becomes  mislaid,  the 
only  record  is  that  the  grade  has  been  changed.  Whatever  the  in- 
strument that  makes  the  change,  the  figures  of  the  new  grade 
should  appear  .on  its  face,  so  that  if  any  record  of  the  c'hange  re- 
main, there  shall  be  no  question  as  to  what  it  is. 

It  can  be  laid  down  as  a  fundamental  principle  that  the  ele- 
vations should  be  so  fixed  that  there  shall  be  no  question  in  the 
mind  of  any  engineer  as  to  the  established  grade  of  any  piece  of 
property,  its  exact  elevation  being  simply  a  mathematical  calcula- 
tion. 

Grades  in  some  cities  are  established  by  fixing  the  elevation  of 
•  the  streets  at  the  centre  of  the  intersections  and  at  such  points  be- 
tween the  streets  where  it  is  desired  to  make  a  break  in  the  grade. 
A  strict  interpretation  of  this  would  establish  the  elevation  of  the 
pavement  only,  leaving  the  curbs  to  be  set  according  to  the  ideas 
of  any  engineer  or  surveyor  who  should  happen  to  be  called  in  to 
fix  the  curb-grades.  On  level  surfaces  or  light  slopes  this  would  not. 
be  so  objectionable,  but  on  steep  hillsides,  where  the  prevailing 
grade  is  4  per  cent,  there  will  be  a  difference  of  1.2  feet  between  the 
elevation  of  the  centre  of  the  street  opposite  the  two  curbs  of  an 
intersecting  street  having  a  roadway  30  feet  wride.  And  if  the 
curb-elevations  should  be  made  the  same,  there  would  be  an  equal 
difference  between  the  sides  of  the  cross-streets  which  is  excessive, 
and  should  not  be  allowed.  The  engineer  then  would  be  called 
upon  to  use  his  judgment  and  settle  for  himself  the  exact  eleva- 
tions of  the  curb-corners.  Acting  in  this  way  in  determining  the 
building-grade  for  a  piece  of  property  situated  midway  of  the  block, 
it  would  be  a  coincidence  merely  if  he  should  fix  upon  the  exact 
elevation  as  finally  determined  when  the  street  came  to  be  im- 
proved. This  is  certainly  a  bad  method.  It  is  the  curb-grade  that 
fixes  the  grade  at  the  building-line,  and  that  is  the  only  point  that 
interests  the  property  owner. 

If,  however,  the  elevation  of  cadi  curb-corner,  as  well  ag  all 
breaks  in  the  grade,  is  defined  by  ordinance,  there  can  be  no  mis- 
understanding, and  the  grade  in  front  of  all  property  may  be 
definitely  calculated. 


WIDTH  OF  STREETS  AND  KO  AD  WAYS,  ETC. 


485 


If,  however,  the  gradient  much  exceed  3  per  cent,  complications 
will  often  arise  at  the  property-line  corners. 

Take,  for  instance,  a  case  as  illustrated  in  Fig.  60,  where  the 


15' 


40.9 


30 


J5 


•*  FIRST 


ST 


39.1 


39.1 


41.23 


FIG.  60. 

elevation  at  the  curb-corners  is  40.0  and  the  grades  rise  from  the 
intersection  in  two  directions  at  the  rate  of  6  per  cent,  and  fall  in 
the  other  direction  at  the  same  rate. 

The  elevation  of  the  curb  on  West  Street  opposite  the  corner 
A  will  be  40.9,  while  on  First  Street  opposite  the  same  corner  it 
will  be  39.1,  and  the  property-grade  for  the  corner  A  as  obtained 
from  these  elevations  by  adding  .33,  the  standard  sidewalk  slope, 
will  be  41.23  and  39.43  for  the  same  point.  This  will  create  a 
great  deal  of  trouble  and  confusion;  especially  if  the  street  be  un- 


486        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

improved  and  the  architect  plans  his  building  from  the  grade  of  the 
street  upon  which  is  the  main  entrance. 

To  overcome  this  a  break  of  grade  should  be  made  at  the  prop- 
erty-line whenever  the  rate  of  grade  exceeds  2  per  cent.  A  grade  of 
2  per  cent  on  an  intersection  insures  a  maximum  difference  of  0.6 
at  A  when  the  sidewalk  width  is  15  feet  as  in  the  figure.  When 
this  width  is  more  or  less  than  15  feet  the  rate  of  grade  should  be 
modified  so  that  in  no  case  shall  there  be  a  greater  difference  in 
property-line  grades  as  calculated  above  than  0.6  of  a  foot.  This 
difference  can  be  reduced  to  a  minimum  by  reducing  the  standard 
slope  of  the  sidewalk  on  one  side  and  increasing  it  on  the  other. 
On  residence  streets  where  buildings  set  back  from  the  street  this 
rule  can  be  somewhat  modified. 

The  following  is  recommended  as  a  form  for  arranging  curb- 
elevations  in  grade  ordinances,  the  body  of  the  ordinance  specify- 
ing that  the  grade  shall  be  a  straight  line  between  given  points: 

GRADE  OF  FIRST  STREET. 

Elevation  of  Elevation  of 

East  Curb.  West  Curb. 

North  curb  of  South  West  Street 22.0  22.0 

South  property-line  of  West  Street 39.1  39.1 

South  curb-line  of  West  Street 40.0  40.0 

North  curb-line  of  West  Street 40.0  40.0 

North  property-line  of  West  Street 40.9  40.9 

A  point  200  feet  north  of  line  of  West  Street. .  52.9  52.9 

South  property-line  of  North  West  Street 60.9  60.9 

South  curb-line  of  North  West  Street 61.2  61.2 

The  above  method  has  been  used  successfully  at  Omaha,  Neb. 


CHAPTER    XV. 

/ 

ASPHALT    PLANTS. 

THE  machinery  used  for  the  preparation  of  the  asphalt  mix- 
ture is  technically  termed  the  plant.  Its  province  is  to  take  the 
•different  materials  and  mix  them  in  the  proper  proportions  for  the 
pavement,  and  the  arrangement  that  will  properly  do  this  the 
most  cheaply  and  expeditiously  is  the  best. 

When  it  is  understood  just  what  is  required  of  the  plant,  it  is 
simply  a  problem  in  mechanical  engineering  as  to  its  exact  design. 

Like  all  machinery  a  large  first  cost  means  a  small  outlay  for 
operation  and  maintenance.  But  some  contractors  prefer  to  carry 
out  details  by  manual  labor  rather  than  by  machinery,  giving  as  a 
reason  that  it  is  less  liable  to  cause  delay  and  in  the  end  is  more 
economical.  All  details  must  be  governed  by  circumstances  and 
the  conditions  of  each  case. 

Before  taking  up  methods  of  construction,  it  will  be  well  to 
discuss  somewhat  the  capacity  and  location  of  the  plant,  the  two 
being  associated  more  or  less,  especially  in  cities  that  cannot  be 
supplied  from  one  location. 

Capacity. 

In  cities  of  150,000  or  even  200,000  inhabitants  there  is  no 
necessity  for  more  than  one  plant  from  an  economical  standpoint. 
Where  different  companies  are  operating  in  the  same  city,  each 
must  have  a  plant  of  its  own;  but  it  is  proposed  to  discuss  the 
question  with  a  view  to  providing  for  a  community  as  economically 
as  possible,  for  the  time  may  come  when  municipalities  will  lay 
asphalt  pavements.  New  York  City  has  agitated  the  question,  and 
Toronto  is  now  considering  it. 

Assuming  that  weather  conditions  will  permit  asphalt  to  be 

487 


488        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

laid  from  the  first  of  May  to  the  first  of  December  of  each  year,, 
and  that  there  will  be  twenty  days  per  month  suitable  for  work, 
there  will  be  140  working  days  each  season,  and  a  plant  having  an 
output  of  1000  square  yards  per  day  would  lay  140,000  yards  per 
year.  This  would  be  as  much  as  would  be  often  required  in  a  city 
of  the  size  mentioned  above.  It  is  perfectly  practicable,  however, 
to  construct  one  of  greater  capacity,  and  it  is  a  matter  of  record 
that  one  Brooklyn  plant  laid  250,000  square  yards  of  pavement  in 
1897.  When,  however,  such  an  amount  is  laid,  the  hauls  in  many 
instances  must  be  excessive  and  then  there  comes  up  the  ques- 
tion of 

Location. 

This  is  not  decided  simply  by  the  streets  to  be  paved.  All 
material  used  must  first  be  taken  to  the  plant,  and  as  sand  forms 
about  85  per  cent  of  the  entire  wearing  surface,  the  question  of  its 
supply  becomes  an  important  factor  in  determining  the  location. 
If  sand  must  be  brought  from  outside,  a  plant  near  the  railroad 
or  water-front  is  almost  a  necessity. 

The  price  of  real  estate  must  often  be  taken  into  considera- 
tion, as  what  would  otherwise  be  an  ideal  location  might  be  pro- 
hibitive on  account  of  the  fixed  charges  if  the  cost  of  the  necessary 
land  should  be  too  great. 

There  is  also  a  certain  amount  of  dust  in  and  around  every 
asphalt  plant,  and  if  located  in  the  vicinity  of  expensive  ma- 
chinery, enough  damage  may  be  done  to  cause  a  nuisance. 

There  has  been  one  case  of  the  removal  of  a  plant  from  a  de- 
sirable locality  simply  on  account  of  the  destruction  to  machinery 
in  adjoining  buildings  by  the  dust  being  carried  into  open  win- 
dows. 

Territory  within  2J  miles  from  the  plant  can  be  economically 
supplied  with  material.  Working  ten  hours  per  day,  an  ordinary 
team  will  haul  four  loads  for  that  distance;  but  if  the  haul  be 
much  increased,  the  loads  would  be  reduced  to  three  and  the  cost 
of  hauling  correspondingly  increased. 

Assuming  the  wages  of  a  team  to  be  $5  per  day  and  that  each 
load  will  lay  33  square  yards  of  surface,  at  four  loads  per  day  the 


f 

ASPHALT  PLANTS.  489 

cost  of  hauling  will  be  3.8  cents  per  yard  for  surface  and  1.9  cents 
for  binder,  or  5.7  cents  complete.  With  three  loads  per  day  per 
team  the  cost  would  be  7.6  cents  per  yard.  Where  but  a  small 
amount  of  work  is  projected  outside  of  the  2J-mile  limit,  the  extra 
expense  would  not  be  much,  but  in  establishing  more  than  one 
plant  in  the  same  city  it  should  be  seriously  considered. 

It  is  probable,  however,  in  making  a  final  decision  upon  a  loca- 
tion, that  the  governing  principles  will  be  cost  of  real  estate  and 
the  facility  for  receiving  the  crude  material. 

The  actual  work  to  be  performed  by  the  plant  is  heating  the 
sand  and  stone  for  binder,  making  the  asphaltic  cement,  and  some- 
times the  stone-dust,  and  mixing  these  different  ingredients  in 
their  proper  proportions. 

Heating  the  Sand. 

This  is  an  important  function.  To  lay  1000  square  yards  of 
pavement  will  require  approximately  60  cubic  yards  of  sand  and 
30  cubic  yards  of  stone  for  binder.  The  plant  should  have  a 
capacity  somewhat  in  excess  of  that  amount,  so  that  a  stoppage  of 
a  few  hours  would  not  interfere  with  the  supply  for  the  mixer. 
As  sand  retains  its  heat  when  in  bulk  for  a  long  time,  no  loss  en- 
sues from  the  storage  of  quite  an  amount. 

Sand  comes  to  the  plant  as  a  rule  damp  and  often  wet.  A1F 
moisture  must  be  evaporated  and  the  material  brought  to  a  tem- 
perature of  400°.  The  sand  should  be  heated  as  uniformly  as  pos- 
sible, for  if  any  portion  be  too  hot,  it  is  liable  to  burn  and  injure 
the  asphalt  even  when  the  average  temperature  would  be  satis- 
factory. Just  what  temperature  asphalt  will  stand  without  injury 
is  not  positively  known,  but  there  is  no  necessity  of  heating  it  much 
above  400°  F. 

The  sand  is  generally  heated  in  hollow  steel  cylinders  or  drums 
set  at  a  slight  vertical  angle.  Upon  the  inside  of  the  cylinder  angle- 
irons  are  bolted  at  intervals.  The  cylinder  is  set  in  a  solid  frame 
and  surrounded  by  an  iron  jacket.  The  heat  is  applied  to  the  space 
inside  the  jacket  and  the  cylinder  revolved.  The  sand  is  carried 
on  the  angle-bars  up  the  side  of  the  cylinder  for  a  certain  dis- 
tance, when  it  falls  to  the  bottom,  is  again  carried  up,  the  operation 


'490        STREET  PAVEMENTS  AND  PAVING    MATERIALS. 

being  continued  as  long  as  the  sand  remains  in  the  drum.  The 
drum  being  set  at  an  angle,  the  sand  falls  vertically  and  advances 
towards  the  lower  end  a  distance  equal  to  the  sine  of  the  vertical 
angle.  The  time  sand  is  retained  in  the  drum  is  regulated  by  the 
rate  of  its  revolutions.  In  addition  to  the  above  the  capacity  of 
the  sand  drum  will  be  governed  by  its  diameter  and  length. 

Some  heaters  are  constructed  on  a  somewhat  different  plan,  the 
heat-space  being  in  the  centre  of  the  drum,  and  the  sand  falling 
directly  upon  the  heated  cylinder.  The  other  details  are  practically 
as  given  above.  An  attachment  is  made  by  which  all  dust  and 
steam  are  carried  off. 

As  the  heated  sand  is  delivered  at  the  end  of  the  drum,  it  is 
carried  by  elevators  to  the  storage-bin  on  the  mixing-platform. 


Asphaltic  Cement. 

To  lay  1000  Square  yards  of  pavement  will  require  approxi- 
mately 25,000  pounds  of  asphaltic  cement  made  from  Trinidad 
asphalt  is  melted  in  kettles  and  the  petroleum  residuum  or  other 
ilux  is  then  added.  As  a  different  amount  of  flux  is  used  for  the 
binder  cement,  separate  sets  of  kettles  will  be  necessary  for  econom- 
ical operation.  Three  kettles  should  be  provided  for  the  surface 
mixture  and  two  for  the  binder.  As  it  requires  about  eight  hours 
to  thoroughly  mix  the  oil  and  asphalt,  as  soon  as  one  kettle  is 
emptied  it  should  be  immediately  refilled  so  that  there  will  always 
be  some  cement  ready  for  use. 

The  mixing,  or  agitating  as  it  is  generally  called,  is  done  me- 
chanically and  also  by  means  of  air. 

The  mechanical  method  consists  simply  of  an  arrangement  by 
which  what  is  practically  a  paddle-wheel  is  revolved  in  the  kettle, 
keeping  the  material  in  constant  motion. 

With  the  air  process  a  series  of  perforated  pipes  are  laid  in 
and  around  the  inside  of  the  kettles.  By  means  of  a  pump  air  is 
forced  into  these  pipes  and  through  the  perforations  to  the  surface, 
thoroughly  mixing  the  oil  and  asphalt.  It  is  extremely  important 
that  these  two  ingredients  become  thoroughly  incorporated  with 
each  other,  so  that  the  flux  shall  act  upon  all  the  asphalt,  convert- 


I 

ASPHALT  PLANTS.  491 

ing  it  into  a  homogeneous  compound.  After  the  cement  has  been 
thoroughly  mixed  it  should  not  be  allowed  to  stand  for  any  length 
of  time,  lest  there  may  be  some  separation  of  the  oil  and  asphalt, 
but  kept  constantly  in  motion  until  used. 

Care  should  be  exercised  also  when  the  bottom  of  the  kettle 
is  approached,  to  see  that  the  cement  still  contains  its  proper 
quantity  of  bitumen.  This  is  particularly  important  in  asphalts 
containing  a  large  amount  of  impurities.  A  failure  to  observe  this 
caused  a  mixture  to  be  sent  upon  the  street  that  contained  but  4 
per  cent  of  bitumen.  In  this  particular  instance  the  discrepancy 
was  so  great  that  it  was  easily  detected  by  the  inspector;  but  had 
it  been  somewhat  less,  or  the  inspector  inattentive,  another  inex- 
plainable  failure  of  an  asphalt  pavement  would  probably  have  been 
reported. 

Stone-dust. 

In  some  localities  pulverized  limestone  cannot  easily  be  ob- 
tained, BO  that  a  mill  for  grinding  it  is  necessary.  This  involves 
an  extra  expense  in  the  construction  of  the  plant,  and  where  the 
stone-dust  can  be  obtained  in  the  market  it  will  generally  be 
cheaper  to  purchase  it.  The  amount  used  per  square  yard  of  pave- 
ment is  about  14  pounds. 

Mixing. 

Having  the  different  ingredients  already  prepared,  the  next 
step  is  the  process  of  mixing  itself.  The  mixer  consists  of  an  iron 
box  having  a  capacity  of  about  8  cubic  feet.  Through  the  bottom  of 
the  box  run  two  parallel  shafts  about  eighteen  inches  apart,  to  which 
are  attached  steel  blades  some  twelve  inches  long  and  four  inches 
wide,  set  at  an  angle  of  about  30°  to  the  shaft.  The  shafts  revolve 
in  opposite  directions,  the  blades  meshing  into  each  other,  thor- 
oughly mixing  the  material  in  a  very  short  time.  The  bottom  is 
made  up  of  two  pieces  opening  by  means  of  a  lever  from  the  centre, 
so  that  the  mixture  drops  into  the  wagon  or  cart  waiting  below. 
This  part  of  the  machinery  is  located  on  a  platform  high  enough 
to  permit  a  team  to  drive  under  to  receive  the  charge. 

In  the  early  plants  sand  was  shovelled  into  an  iron  bucket  con- 
taining the  right  quantity,  hung  on  an  overhead  trolley,  and  then 
pushed  .by  hand  to  the  mixer  and  dumped.  The  asphaltic  cement 


492        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

is  then  dipped  from  the  kettle  into  a  smaller  bucket,  weighed,  and 
then  conveyed  to  the  mixer  by  another  trolley,,  where  it  is  poured 
upon  the  sand  and  the  mixing  continued  until  it  is  entirely  com- 
pleted, the  actual  time  consumed  being,  on  an  average,  70  seconds. 
The  binder  is  mixed  in  a  similar  manner  in  a  separate  mixer. 

In  more  recent  plants  sand  is  stored  in  a  bin  directly  over  the 
mixer,  so  that  by  pulling  a  slide  the  proper  amount  can  be  dropped 
into  the  box  without  extra  labor,  and  by  means  of  compressed  air 
the  asphaltic  cement  is  conveyed  to  the  mixer  and  the  required 
amounts  drawn  off  by  opening  and  closing  a  valve.  This  re- 
quires less  labor  for  the  operation  and  has  proven  very  success- 
ful. 

While  the  question  of  plant  has  been  discussed  from  the  stand- 
point of  1000  yards  per  day,  its  capacity  can  be  easily  increased  by 
increasing  the  size  of  the  mixing-box  as  well  as  the  number  and 
size  of  the  melting-kettles.  In  the  larger  plants  of  recent  date 
the  mixing-box  has  been  made  large  enough  to  contain  16  cubic 
feet  instead  of  8,  and  as  the  time  required  for  mixing  is  practically 
the  same,  the  capacity  of  the  plant  is  consequently  doubled  if  the 
other  parts  have  been  increased  correspondingly. 

Assuming  that  the  actual  time  of  mixing  is  70  seconds,  but 
that  one  charge  only  will  be  prepared  every  2%  minutes,  the  plant 
will  turn  out  in  ten  hours  240  charges.  The  charge  from  the 
8-foot  box  will  lay,  approximately,  4J  square  yards  of  wearing  sur- 
face, and  from  a  16-foot  box  9  square  yards,  giving  as  the  actual 
capacity  of  the  plant  1080  and  2160  yards,  respectively,  per  day. 

Cost. 

In  estimating  the  cost  of  an  asphalt  plant  the  necessary  build- 
ings and  real  estate  will  not  be  considered,  as  so  much  variation 
can  be  made  in  the  construction  of  the  one,  and  the  cost  of  the 
other  varies  so  greatly  in  different  cities.  There  is  also  a  great 
difference  in  the  actual  cost  of  installing  an  asphalt  plant,  depend- 
ing upon  its  capacity  and  exact  method  of  construction.  If,  as 
has  been  said  before,  a  large  amount  of  machinery  be  used,  the 
first  cost  will  be  increased,  but  the  expense  of  operating  will  be 
small.  A  satisfactory  plant  with  a  capacity  of  1000  yards  per 
day  can  be  built  under  ordinary  circumstances  for  $12,000,  while 


ASPHALT  PLANTS.  493 

<one  of  double  its  capacity,  with  all  the  modern  and  improved  ma- 
chinery, should  cost  not  to  exceed  $25,000.  The  number  of 
employees  necessary  to  operate  a  plant  will  range  from  nine  to 
twenty,  according  to  size  and  manner  of  construction.  One  mod- 
ern plant,  with  a  capacity  of  1200  yards  per  day,  has  been  operated 
by  ten  people,  including  foreman,  timekeeper,  etc. 

Portable  Plants. 

When  the  asphalt-pavement  industry  was  in  its  infancy,  and 
for  many  years  thereafter,  it  was  not  considered  practicable  to  lay 
asphalt  pavements  in  cities  of  small  size  on  account  of  the  ex- 
pense of  the  plant.  But  as  this  pavement  came  into  general 
favor  and  the  demand  for  it  became  greater,  even  in  the  smaller 
cities,  attempts  were  made  to  construct  portable  plants  that  could 
be  transported  easily  and  cheaply  from  one  city  to  another.  After 
many  trials  this  was  successfully  accomplished. 

The  Hetherington  Railway  Plant  in  Indianapolis,  Ind.,  is  one 
that  has  been  successfully  used.  This  plant  is  entirely  contained 
upon  two  railway  cars,  one  of  these  being  called  the  dryer-car,  and 
the  other  the  melting-car.  The  cars  are  built  substantially  of 
steel  and  fitted  with  automatic  couplers  and  air-brakes,  and  in 
every  respect  are  made  conformable  with  master  car-builders' 
rules,  so  that  they  can  be  used  upon  all  railroads.  Upon  the 
Jryer-car  is  established  a  steam-boiler.  Alongside  the  boiler  upon 
the  deck  of  the  car  is  located  the  engine  to  furnish  power.  Upon 
this  car  there  are  an  air-compressor  or  blowing-engine,  a  boiler 
feed-pump  in  addition  to  the  injector,  a  double  rotary  exhauster, 
link-belt  elevator  for  shovelling  sand  on  the  drums,  and  another 
for  conveying  away  this  sand  after  it  has  been  heated.  There  is 
also  established  upon  this  car  a  pair  of  compact  and  efficient  ro- 
tary drums  for  heating  sand  as  required.  The  sand-drums  consist 
of  two  cylindrical  shells  of  medium  diameter  suspended  in  air  for 
the  proper  setting  or  housing  of  steam,  and  suitable  furnace  with 
hot-air  chambers. 

It  was  found  that  by  using  the  two  drums  arranged  as  de- 
scribed, exposed  to  the  radial  action  of  the  heat,  a  greater  num- 
ber of  square  feet  of  drum  surface  could  be  obtained  in  a  rea- 
sonably small  space  than  by  any  type  of  single-drum  dryer. 


494=        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

Instead  of  following  the  old  plan  of  setting  drums  in  an 
inclined  plane  in  order  to  cause  the  sand  to  travel  from  one  end 
to  the  other,  these  drums  are  set  horizontally,  with  a  spiral  con- 
veyor, attached  to  the  inner  surface  of  the  shells,  carrying  the- 
sand  from  one  end  to  the  other.  The  sand  is  fed  to  the  drums  by 
a  conveyor-screw.  The  heat  for  heating  the  sand  is  generated  in 
a  furnace  under  the  drums,  coal,  oil,  gas,  wood,  or  coke  being 
used  as  fuel.  The  heat  from  the  fires  travels  the  full  length  of 
the  drums  along  the  under  side,  and  then  again  passes  the  full 
length  of  the  drums,  but  within  the  shells,  thus  utilizing  the  full 
amount  of  the  heat  that  is  generated  in  the  most  economical  man- 
ner. 

The  melting-car  contains  kettles  for  melting  the  asphalt  and 
making  asphaltic  cement,  as  well  as  the  sand  storage-bin  and 
actual  mixers.  In  this  plant  the  agitating  is  done  mechanically 
or  by  compressed  air,  or  by  both  as  may  be  desired.  When  both 
methods  are  used,  the  material  is  first  melted  in  an  open  kettle, 
when  it  is  transferred  by  a  vacuum  process  to  the  mechanical  agi- 
tator which  is  closed.  In  this  system  the  air-engine  is  so  arranged 
that  it  may  be  used  both  for  pumping  air  from  the  closed  agitator 
and  for  pumping  air  into  it.  The  agitator  is  in  this  case  an  air- 
tight vessel  or  kettle,  provided  with  mechanical  means  for  stirring. 
The  vessel  has  connection  by  means  of  a  large  steam-jacketed 
pipe  with  the  open  kettles  of  the  system.  When  the  agitator  is 
to  be  filled  a  cock  is  opened  in  the  pipe  and  the  air-pump  begins 
to  exhaust  the  air  from  the  tight  vessel  or  agitator.  As  this  air 
is  withdrawn,  the  melted  asphalt  in  the  open  kettles  rushes  in  ta 
take  its  place..  When  all  of  the  asphalt  has  passed  from  the  open 
kettle  into  the  closed  agitator,  the  cock  is  again  closed  and  the 
pump  ceases  operation.  After  the  asphalt  has  been  sufficiently 
stirred  and  mixed,  it  is  forced  through  the  proper  steam-jacketed 
pipes  from  the  agitator  to  the  mixer,  where  it  is  drawn  off  into  a 
measuring-vessel  as  needed. 

When  ready  for  travel,  the  plant  presents  an  appearance  much 
like  two  ordinary  freight-cars,  but,  as  in  the  case  of  a  permanent 
plant,  the  mixing  has  to  be  done  at  a  sufficient  height  to  allow 
teams  to  drive  under  the  mixer  and  receive  the  charge  direct. 

In  operation,  the  asphalt  is  melted  and  prepared  in  a  small 


ASPHALT  PLANTS. 


495 


kettle,  and  sand  is  shovelled  into  the  box  of  the  cold-sand  eleva- 
tor. This  delivers  the  sand  into  the  heating-drums,  from  which 
it  passes  into  the  boot  of  the  enclosed  hot-sand  elevator,  by  which 
it  is  carried  up  to  the  screen  and  then  falls  into  the  tempering- 
bin.  By  using  an  overhead  screen  the  refuse  can  be  carried  away 
by  a  chute  without  having  to  be  rehandled.  While  the  sand  is 
being  heated,  the  asphalt  is  ready  melted  in  the  kettles  and  thor- 
oughly stirred  with  a  c}rlindrical  agitator.  The  materials  being  all 
ready,  the  operator  of  the  melting-car  opens  a  valve  under  the 
asphalt  pipe-line  and  allows  a  certain  amount  of  asphalt  to  flow 
into  the  receptacle  in  which  it  is  measured.  At  the  same  time  the 
operator  at  the  mixer  allows  the  hot  sand  and  carbonate  of  lime  to- 
fall  on  the  mixer.  The  compact  asphalt  is  poured  into  it  and  the 
whole  mass  is  thoroughly  stirred  for  a  limited  period.  The  opera- 
tor then  pulls  a  lever  which  opens  a  door  at  the  bottom  of  the 
mixer  and  allows  the  charge  to  flow  into  the  wagon  standing  be- 
tween the  cars. 

This  and  other  plants  built  on  somewhat  the  same  order  have 
been  in  use  for  a  number  of  years,  and  of  a  capacity  sufficient  to 
lay  from  1250  to  2000  square  yards  per  day. 

The  following  tables  are  given  to  show  the  varying  amounts  of 
bitumen  in  different  asphalts. 


TABLE  No.  72. 

ANALYSES   OF  ASPHALTS  FROM   DIFFERENT  SOURCES. 


Water. 

Bitumen 

Other 
Organic 
Matter. 

Mineral 
Matter. 

Total. 

Peiro- 
lenn. 

Asphalt- 
ene. 

Trinidad  asphalt,  crude.  .  .  . 
Cuban  asphalt  

2.03 
0.39 

32.45 
25.46 
35.09 
8.52 
7.49 
8.79 
3.35 
11.32 

4.39 

22.11 
54.41 
63.18 
3.92 
4.32 
3.27 
2.42 
3.81 

2.83 

8.12 
2.47 
1.73 
25.79 

35.29 
17.03 

'ei'.ie' 

88.20 
87.95 
94.23 
83.41 

88.65 

100.00- 
99.76 
100.00 
99.  9& 
100.01 
100.01 

100.  oa 

99.99 
99.97 

Val  de  Travers  asphalt 

Texas,  Uvalde  Co.,  asphalt.. 
Kentucky  asphalt  

i.ia* 

4.10 

California  Sand-rock  asphalt 
*Asphalt  pavement,  Buffalo, 
XT  

0.33 

*  Same  composition  as  the  Delaware  Avenue  pavement. 


496        STREET  PAVEMENTS  AND  PAVING  MATERIALS. 

TABLE  No.  73. 

ANALYSES   OP   DIFFERENT   ASPHALTS    TAKEN     FROM   A   REPORT   MADE   TO   THE 
MAYOR  OF  NEW   YORK  BY  THE  COMMISSIONERS   OF  ACCOUNTS,  MAY   1899. 


Name. 

Bitumen 
Present. 
Per  cent. 

Water. 
Per  cent. 

Mineral 
Matter,  etc. 
Per  cent. 

Nearly  100 

(  „ 

(  „, 

pure 

]  Trace 

j  Trace 

99  286 

0  714 

97.779 

« 

2  221 

Standard  asphalt,  California  

91.680 

6  51 

1  810 

68.060 

31  940 

Refined  Trinidad  pitch  

56.973 

43.027 

Trinidad  pitch,  crude  

39.249 

27.000 

33.751 

AMERICAN  ROCK  ASPHALTS. 
Utah  rock  asphalt,  lime  

43  800 

56  200 

Texas    Uvalde  Co.    rock  shells  .... 

12  5 

Trace 

87  5 

Texas,  Montague  Co.,  rock  sand  

9  139 

(i 

90  861 

11  442 

f, 

88  558 

Indian  Territory,  rock  lime  

8  toll 

it 

89  to  92 

EUROPEAN  ROCK  ASPHALTS. 
Limmer  rock  chalk  

14.30 

85.70 

Lobsam  rock  chalk  

12.32 

i< 

87.68 

Seyssel  rock  chalk  

11  802 

<4 

88  198 

Val  de  Travers  rock  chalk  

10  15 

fi 

89  85 

8  92 

« 

91  08 

Refined  Trinidad  asphalt  contains  about  10  per  cent  of  organic  matter  not 
bitumen. 

Trinidad  crude  asphalt  contains  about  7^  per  cent  of  organic  matter  not 
bitumen. 

In  other  varieties  a  trace  only  of  such  organic  matter  is  found. 


INDEX. 


PAGE 

Abrasion  test  for  paving-brick,  charge  for 267 

conditions  of 267 

machine  for 266,  268 

Abrasion  test  for  stone,  description  of 359 

results  of •. . . . .  360 

Absorption  test  for  paving-brick,  method  of  conducting 272 

preparation  for 270 

results  of 271,  272 

value  of 273 

Accidents  on  pavements .' 161,  162 

Albany,  early  pavements  of 13 

Alternative  bids,  objections  to 381 

Amphibole 15 

Analysis  of  asphalt:  Asphalto 65 

Bechelbronn 51 

Barbadoes 496 

Bermudez 71,  496 

Cuban 495 

Dead  Sea '495 

Indian  Territory 496 

Kentucky 495 

Mexican 54,  69,  70,  496 

Rock 68,  495,  496 

Texas 74,  75,  495 

Table  of 495,  496 

Trinidad 54,  60,  61,  495,  496 

Utah 76,  496 

bluestone 30 

IS  cement,  natural 100 

Portland , 99 

clay 85 

fire-clay 85 

gilsonite 48 

497 


498  INDEX. 

PAGE: 

Analysis  of  granite,  Barre  (Vt.) 23 

Blue  Hill  (Maine) 2£ 

Exeter,  California 25> 

Milford,  Mass 2g 

North  Jay,  Me 23 

Petersburg,  Va 24 

Port  Deposit,  Md 21 

Quincy,  Mass 24 

Waterford,  Conn 22 

kaolin 80,  86 

lime 3& 

limestone  and  resulting  limes 3& 

Bedford 37 

from  various  localities 39 

Trenton 38 

Maltha 63 

Material  for  cement 133. 

paving-brick 260 

porphyry 86- 

sandstone,  Berea 3& 

Colorado. 34 

shale 85- 

trap-rock,  Birdsborough,  Pa 26 

Meriden,  Conn , 26 

Monson,  Mass 26 

New  Jersey 27 

Appian  Way 2 

Artificial-stone  blocks l41 

Asphalt,  analysis  of,  Endemann's  method 53 

Linton's  method ....  5& 

Richardson's  method 52 

Sadtler's  method 5£ 

artificial,  Day's  experiment  with 47 

Asphalto  fluxing 66 

refining. 66 

Barbadoes,  analysis  of ,-  •  •  •  496 

description  of 78- 

Bechelbronn,  analysis  of 51 

Bermudez,  analysis  of 7t 

description  of 71 

first  used  in  pavement 71 

location  of "0 

California,  analysis  of 6H 

bitumen  in . 228 

description  of 63,  6& 


INDEX.  499 


Asphalt,  California,  first  used 62 

location  of 63,  65 

character  of 219 

comparison  of  different  kinds 55 

cost  of 250 

Cuban,  analysis  of 495 

description  of 77 

Dead  Sea,  analysis  of 495 

description  of 78 

definition  of 42,  44 

Egyptian,  description  of 79 

formation  of 44,45,49 

how  tested 220 

Indian  Territory,  analysis  of 496 

bitumen  in  76 

description  of 76 

Kentucky,  analysis  of 495 

analysis  of  rock  containing 72 

bitumen  in 72 

description  of 72 

preparation  of 72 

used  in  pavements 73 

location  of 56 

Mexican,  analysis  of 69,  70,  496 

description  of 69 

location  of 69 

Montana 77 

petroleum 64 

rock  of  California,  description  of 66 

location  of 66 

rock  of  Europe,  analysis  of 68 

bitumen  in 68 

formation  of 67 

location 67 

Syrian 78 

suitable  for  pavements... 219 

terms  for 40 

Texas,  analysis  of 74,  75,  495 

location  of 73 

preparation  of 73 

uses  of 74 

Trinidad,  analysis  of 54,60,61 

bitumen  in 228 

how  mined 58 

location  of 57 


500  INDEX. 


PAGE 

Asphalt,  Trinidad,  refining  of 60,  61 

Turkey 78 

Utah,  analyses  of 76,  49fr 

description  of 7~> 

quantity  of 75, 

value  of  analyses 55. 

Asphalt  block  pavement :  advantages  of 256 

amount  of 256 

blocks,  how  made 255 

how  laid.   256,  413 

sizeof 256,413 

cork  blocks,  cost  of 257 

where  laid 257 

cost  of 256 

first  laid 255- 

in  Poughkeepsie 164 

specification  for:  blocks,  composition  of 413 

covering  for 414 

how  laid 413 

size  of 413 

Asphaltene,  description  of , , 51 

formula  for 52,  54 

Asphaltic  cement :  amount  in  pavement 229,  250,  490 

as  a  liquid 225 

fluxes  for 220,  221,  222 

hardness,  how  tested 223 

in  Washington 224 

how  prepared 220,  490 

Asphaltina :  cement,  composition  of ,  .  254 

description  of 253 

pavement,  cost  of 255 

mixture 255 

specifications  for 254 

Asphalt  macadam,  first  used 8 

Asptialt  pavement:  American,  in  Europe , 252 

binder  for,  action  of  water  on 233 

composition  of 230 

object  of 230 

size  of  stone  for 231 

thickness  of 230,  397 

cost  of 250,  251 

cracks  in 238 

caused  by  what 23S 

effect  of 239 

how  formed . .  . .    239 


INDEX.  501 

PACK 

Asphalt  pavement :  cracks  in,  how  prevented 238 

cross-section  of 235 

table  for  laying  out 218 

damaged  by  fire 240 

effect  of  illuminating-gas  on 239 

appearance  of 240 

first  laid:  London 7 

New  York 10 

Paris 8 

United  States 215 

Washington 215 

foundations  for:  bituminous 231 

broken  stone , 232 

cobblestone 232 

necessity  of 231 

stone  block 232 

grades  of 216^  217,  218 

gutters  for,  how  laid 237 

material  far 237 

how  laid  against  rigid  surface 236 

in  Cairo 143 

maintenance  of 244,  246,  247 

material  for 225 

method  of  laying 233,  235 

method  of  rolling 234 

amount  of 235 

objections  to 216 

on  bridges 251 

sand  for 226 

size  of,  in  different  cities 227 

slipperiness  of 216 

standard  of  condition  of,  at  expiration  of  guaranty. . . .  240 

temperature  of  air  when  laying  should  be  discontinued  237 

temperature  of  material  when  laid 234 

wearing  surface  of:  aspbaltic  cement  in. 229 

composition  of 227 

laying 283 

mineral  matter  for 228 

requirements  of - 227 

rolling 234 

thickness  of .  229 

weightof 250 

when  too  soft 239 

Asphalt-pavement  specifications : 

binder,  asphaltic  cement  for 39"^ 


502  INDEX. 

PAGE 

Asphalt-pavement  specifications: 

binder,  character  of 397 

how  laid 397 

stone  for 397 

thickness  of 397 

general  requirements  of 402 

maltha  (liquid  asphalt),  how  used 401 

properties  of ; 401 

not  laid  in  wet  weather  403 

rock  asphalt,  amount  of  bitumen  in 402 

how  laid , 401 

temperature  of 402 

wearing  surface,  asphalt,  description  of 398 

asphaltic  cement,  how  made 399 

gutters,  how  treated 4;  1 

how  laid 4(0 

how  prepared 4CO 

mineral  matter,  fineness  of 400 

mixture  for 398 

petroleum  oil,  description  of 398 

proportions  of  material  for 400 

rolling 401 

sand,  size  of 400 

temperature  of 400 

Asphalt  plant :  capacity  of 487 

cost  of 492 

location  of 488 

machinery  for 491 

portable,  capacity  of 495 

demand  for 493 

description  of ^ 493,  494 

province  of , 487 

work  of :  asphaltic  cement,  preparation  of 490 

sand,  how  heated 489 

stone-dust,  preparation  of 491 

time  of  mixing 492 

Asphalt  roads  in  California 12 

Australian  wood  pavements 320 

London 298 

New  York 321 

Baltimore,  early  pavements  of 11 

Barbadoes  asphalt 78 

Basalt,  composition  of ~1 

description  of 20 

Belgian  blocks,  description  of , 180 


INDEX.  503 


PAGE 

Belgian  blocks,  first  used  in  New  York t 180 

material  for -.-.-. 184 

objections  to 185 

specifications  for 185 

Belgian-block  pavement , 9 

cross-section  of 186 

description  of 185 

estimated  cost  of , 187 

how  laid 186 

Berea  sandstone,  analysis  of 33 

location  of 32 

strength  of 33 

Bermudez  asphalt 70 

Bids,  alternative 381 

certified  check  to  accompany 382 

not  to  be  changed  after  opening 383 

not  to  be  received  after  expiration  of  time  limit 382 

to  be  indorsed  with  name  of  bidder 383 

unbalanced 388 

Bidders,  blanks  to  be  provided  for 382 

instructions  to .    '. 382 

notice  to 390 

Binder,  amount  of,  for  broken-stone  pavement 343 

for  asphalt  pavement 230 

macadam  pavement 339 

material  for 340,  345,  350,  368 

Biotite  granite 18 

Bitumen,  amount  of,  in  asphalt 228 

asphalt  pavements 225,  228,  242,  250 

artificial,  how  discovered 56 

as  natural  gas 44 

definition  of 40-43 

derivation  of  word 40,  41 

divisions  of 43 

forms  of,  for  pavements 62,  219 

origin  of  ;  German  theory 46 

Malo's  theory 45 

Mendelejeffs  theory 49 

Moissan's  theory 49 

Peckham's  theory 50 

Torrey's  theory 46 

Wall  and  Sawkin's  theory 48 

Wurtz's  theory 50 

parts  of 51 

refining 64 


504:  INDEX. 


Bitumen,  sand-bearing 53 

solvents  for 55 

transportation  of 64 

Blank  forms  for  bidders 3£  $ 

Blocks:  asphalt,  cork,  size  of 2.~>6 

first  used 355 

size  of 25'i 

Belgian 180,  185 

granite 18a 

first  used 5 

first  used  in  Liverpool 7 

size  of,  in  American  and  European  cities 191 

Medina  sandstone 207 

paving,  of  Rome,  size  of 5 

stone,  for  Blackfriars  Bridge (> 

size  of,  in  Catania,  Italy 179 

European  cities 1 92 

wood,  size  of 294,  295,  320 

Bondi  amount  of,  in  contract 383 

Bonus  for  completion  of  contract 384 

Boston,  early  pavements  of ^0 

Boulevard,  the  first 2 

Brick:  blue,  made  in  England 89- 

early  use  of 88 

fire-clay 85- 

first  used  in  England 89- 

floating 89 

in  pyramid 88 

kiln,  first  in  United  States 8& 

manufacture  of  paving. 90- 

paving,  see  Paving-brick. 

shale 85 

vitrified 8& 

clay  to  produce 87 

test  of 87 

Brick  pavements,  advantages  of 261 

amount  in  United  States 291 

cost  of,  in  American  cities 292 

estimated 292 

cross-section  of 284 

first  laid  in  United  States '. 259= 

foundation  for,  brick  laid  flatwise 282 

broken  stone 28& 

cement  concrete , 283 

plank  and  sand 282; 


INDEX.  505 

PAGE 

Brick  pavements,  in  England 25$ 

in  Holland 258 

life  of 258 

in  Japan 258 

joint-filling  for 284,  286- 

cement  grout ?87 

sand 287 

temperature  of  paving-cement  for 287 

laying,  arrangement  of  brick 289 

breaking  joints 288 

preparing  bed "388 

rolling 288 

testing  for  soft  brick 288 

material  per  square  yard  of 292 

rumbling  of 285 

causes  of 285 

examples  of 285 

how  prevented 286 

Brick  pavements,  specifications  for  :  brick,  how  laid 41 1 

how  tested 411 

in  Philadelphia 291 

St.  Louis 290 

joint-filling  for 412 

size  of 410 

covering  for 413 

Brick  sidewalks,  how  laid 477 

where  laid , , 477 

Bridges,  asphalt  pavement  on 25 1 

expansion-joint  in 252 

Broken  stone,  voids  in 120,  124 

how  reduced 122 

Broken-stone  pavements,  construction  of,  amount  of  rolling  for. .  .338,  341-343 

finishing  surface 346 

foundation  course 337 

cross-section  of 347 

crown  of 344 

drainage  for 334 

foundation  for , 334 

thickness  of 336 

gutters 347 

Macadam's  theory  of 331 

Macadam's  and  Telford's  methods  compared.. 331,  338 

maintenance,  cost  of,  in  Glasgow 370 

London 370 

Marseilles  .  .  371 


506  INDEX. 

PAGE 

Broken-stone  pavements,  maintenance,  cost  of,  in  Paris 370 

Rochester,  New  York  . .   371 

material  for 336 

objections  to t 333 

preparation  of  road-bed 333 

roller  for '. 338 

rolling. 338 

size  and  shape  of  stone  for 330,  336,  337,  P41,  349 

specifications  for  Boston 348 

Brooklyn 349 

Providence 347 

sprinkling 346 

Telford's  method 330 

binding  for 330 

Tresaguet's  method . .   329 

use  of  binder  for 338 

quantity  of 339,  343 

when  first  built  systematically 329 

Broken-stone  roads,  see  Macadam  roads. 

old  methods  of  constructing 332 

size  of  stone  for 330,  332 

thickness  of 3b2 

Burnettizing 328,  324 

effect  of 324 

railway  ties,  cost  of 326 

California  asphalt,  analysis  of 63 

description  of 63 

first  used 62 

for  pavements 62 

location  of 63 

California,  asphalt  roads  in 12 

Carbonate  of  lime  for  asphalt  pavements 227 

Carthaginians,  the  first  road-builders 2 

Cedar-block  pavement,  amount  in  Chicago , . .  313 

in  the  Central  West 311 

life  of 311 

sapless 312 

specifications  for 313 

Cement,  artificial 97 

consumption  of 132 

definition  of 96 

early  use  of 96 

expansion  of,  in  setting 119 

test  for 119 

how  tested..  .   104 


INDEX.  507 

PAGE 

Cement  made  in  United  States 9  T 

natural 9? 

analysis  of 100 

fineness  of 101 

New  York  Building  Code  definition  of 98 

production  of 133 

results  of  tests  on 102 

strength  of 107 

value  of 134 

neat,  and  sand,  tests  of 104 

Portland 97 

analysis  of 99 

of  materials  for 133 

fineness  of 101 

result  of  tests  for 102 

value  of 100 

first  made  in  United  States 97 

first  used 97 

ideal,  composition  of 99 

magnesia,  maximum  amount  in 99 

production  of » 183 

requirements  for 396 

specifications  for 106 

specifications  of  first  patent  for 97 

strength  of 103,  107 

value  of 133 

Roman 97 

Rosendale,  see  Natural 98 

use  of,  in  cold  weather 115,  117 

value  of  long-time  tests  of 104,  105,  106 

Cement  curb,  estimated  cost  of 473 

material  in   472 

specification  for « 47 1 

steel  edge  for 470 

Cement  gutter,  estimated  cost  of 473 

form  of 481 

how  laid 471 

specifications  for 471 

Cement  sidewalks,  estimated  cost  of 479 

how  laid 478 

material  for 479 

specifications  for 478,  479 

Cementitious  value  of  stone 360 

Ceramite  blocks 14:i 

Certified. checks  to  accompany  bids 382 


508  INDEX. 


PAGE 

Certified  checks  to  accompany  bids,  amount  of 383 

Charcoal  roads 293 

Chert  pavement 143 

Chicago,  early  pavements  of 11 

City  engineer  to  bid  on  work 389 

(/lay,  classes  of 83   84 

colored  by 82 

definition  of 80,  82 

fire,  analysis  of 85 

fluxes  of 84 

amount  of 85 

non-plastic 84 

plastic 84 

fusible 84 

high-grade 84 

low-grade 84 

permauance  of  form  in 83 

how  produced 83 

plasticity  of 82,  84,  87 

preparation  of,  for  paving-brick 90,  91,  92 

properties  of 82 

refractory 84 

Cleveland,  early  pavements  of 12 

Coal-tar,  how  discovered  in  asphalt 56 

Coal-tar  pavements  condemned  in  Washington 213 

cost  of  repairs  to 212,  214 

first  laid 211,  212 

life  of 212 

specifications  for 213 

Coal-tar  pitch 197 

Cobblestone  pavement,  amount  in  United  States. 183 

cross-section  of 183 

description  of 182 

estimated  cost  of 184 

foundation  for 1 84 

how  laid 183 

repairs  to 164 

Cobblestones,  size  of. 181,  183 

specifications  for 181,  182 

Colorado  sandstone,  analysis  of 34 

description  of 33 

strength  of 34 

Concrete,  action  of  frost  on 115,  117 

bituminous 212,  213 

composition  of 121 

consistency  of 125 


INDEX.  509 

PAGE 

Concrete,  cost  of 204  472 

definition  of 120 

early  use  of 96 

example  of 120 

hand  and  machine  mixed,  relative  value  of 130 

how  laid 122 

how  mixed 121,  122,  126,  203,  396 

how  protected 205 

machines  for  mixing 126,  127,  129,  130 

material  per  cubic  yard  of 203 

estimated  cost  of 204 

proportions  for 120,  122 

quantity  of  material  in 123,  131,  472 

Concrete  base,  first  used  in  London 7 

first  used  in  New  York 10 

first  used  fur  wood  pavements 294 

Contracts,  bond  for 383 

bonus  for  completing 384 

extra  work  under 380 

indeterminate  quantities  in 380 

let  for  lump  sum 380 

maintenance  clause  in 385,  387 

penalty  for  failure  to  complete 384 

time-limit  of 384 

Cordova,  pavements  of 5 

Cost  of  asphalt-block  pavement 256 

asphalt  pavement 251 

asphaltina 255 

Belgian-block  pavement 187 

brick  pavement 292 

broken-stone  pavement 363 

cobblestone  pavement 184 

granite  pavement , 205,  206 

macadam  roads 362 

Medina  sandstone 208 

wood  pavement 298,  305,  309,  318,  321 

Courtyards,  necessity  of 460 

width  of 462 

Creosote  oil,  amount  of,  per  cubic  foot  of  timber 299,  318 

definition  of 326 

preservative  value  of , 326 

should  contain  naphthalene 326 

Creosoting,   definition  of 323 

Indianapolis  specifications  for 318 

London  specifications  for 299 

value  of,  to  pavement 301 


510  INDEX. 

PAGE 

Cross-breaking  test  for  paving-brick,  method  of  conducting 273- 

reasons  for 274 

value  of 274 

Cross-section   of  asphalt  pavement 235 

Belgian          ««       186- 

brick              "       284 

broken-stone  " 347 

cobblestone    "       183 

granite            " 199 

Cross- walks,  dimensions  of 209,  394 

how  laid 209,  394 

material  for 209,  394 

Crown  of  pavements,  formula  for  laying  out 202 

on  side-hill  streets 201 

principles  for  determining. 200,  201 

table  for 202 

Crushing-test  for  paving-brick,  method  of  conducting 275 

value  of 276. 

Cuban  asphalt 77 

Curbing,  concrete,  see  Cement  curb. 

Curbstones,  cost  of 464,  474 

dimensions  of 394,  463 

foundation  for 395,  466 

amount  of  concrete  for 466 

how  dressed 395,  464 

how  set 464 

limestone  for 467 

material  for. . ; 463 

object  of 462 

radius  of 465 

specifications  for  :  Cincinnati 468 

Liverpool 467 

New  York  City 468 

Rochester 469 

St.  Louis 468 

Cushion-coat  for  asphalt  pavements,  description  of 230- 

objections  to 230 

thickness  of 230 

Cypress-block  pavement  in  Galveston 316 

in  Omaha 311 

life  of 312,  316 

Dead  Sea  asphalt 78 

Diabase  (trap-rock),  formation  of 20 

location  of 20 

Dolomite 35- 


INDEX.  511 


PAGE 

Drainage  of  macadam  streets  and  roads 334,  853 

Early  pavements,  construction  of 178 

cross-section  of 199 

of  Europe 179 

Earth,  composition  of  crust  of 14 

Egyptian  asphalt 79 

Engineering,  School  of,  in  Spain 4 

Estimates  of  cost,  how  made 184 

Evaporation  of  water  from  paving- brick 271 

Expansion-joint  for  asphalt  pavement. ...    239 

asphalt  pavement  on  bridges 252 

brick  pavement 285 

wood  pavement 295,  299,  303,  32 1 

Feldspar,  composition  of 15 

how  destroyed  , 81 

varieties  of 15,  80 

Ferroid 197 

Fineness  of  cement 101 

specifications  for 108 

Fire-clay 84 

analysis  of 85 

Fire-clay  brick 85 

Formula  for  determining  economic  life  of  pavements 155 

for  determining  relative  value  of  paving-brick 277 

for  obtaining  amount  of  traction  on  grades 482 

Foundation  for  asphalt  pavement 231 

Belgian-block  pavement 185 

brick  "        282 

broken-stone          "         335 

cobblestone  "         184 

granite-block         "         191 

macadam  roads 360 

Fusibility  of  clay 84,  85,  87 

Galveston,  wood  pavements  of 316 

Genoa,  streets  of 3 

Gilsonite,  analysis  of 48,  76 

Glass'pavement 141 

Gneiss 19 

Grades,  effect  of 482 

examples  of 483,  485,  486 

for  asphalt  pavements 216 

formula  to  obtain  traction  on 482 

how  established 484 

on  business  streets 482 

steep,  at  intersections 485,  486 


512  INDEX. 

PAGE 

Grades,    steep,  best  pavement  for 483 

Granite,  adapted  for  curbing,  and  pavements 19 

analysis  of 21,  22,  23,  24,  25 

characteristics  of 17 

crushing  strength  of 27 

definition  of 17 

formation  of 17 

properties  of 18 

rift  of 18 

value  of  anual  product  25 

varieties  of 18 

Granite  blocks  :  dimensions  of,  in  American  and  European  cities 191 

principles  determining 189 

first  used 5 

in  Vienna 210 

specifications  for 190 

used  as  toothing-blocks  in  street-car  tracks 457 

wear  of 188 

Granite  pavement :  blocks,  how  laid  at  intersections 193,  194 

how  laid  in 193 

concrete  foundation  for 196 

cross-section  of 199 

estimated  cost  of 206 

foundation  for 191 

preparation  of 192 

in  Vienna 210 

Granite  pavement,  joint-filling  for  ;  ferroid 197 

gravel,  temperature,  and  size  of 198 

Murphy  grout 197 

paving  cement,  amount  per  sq.  yd....  199 

composition  of 197 

temperature  of 205 

Portland  cement 197 

tar  and  gravel 197 

laying 1 96 

material  per  square  yard  of 205 

organization  of  gang  for  laying 205 

ramming,  importance  of 196 

repairs  to 163 

width  of  joints  in 195,  198 

Philadelphia  specifications  for 195 

Granite  pavement  specifications  :  blocks,  classes  of 403 

description  of 403 

how  laid 404 

concrete  foundation 405 


INDEX.  513 

PAGE 

Granite  pavement  specifications:  gravel. 405 

paving-cement,  composition  of 406 

temperature  of 405 

sand,  foundation 404 

sprinkling  with  water 405 

Gravel  for  joint-filling 198 

voids  in 124 

Grass  pavement 140 

Guidet  pavement, 9 

description  of , 181 

size  of  blocks  in 10 

Guaranty  for  asphalt  pavement 240,  386 

brick  " 387 

granite         "         ." 387 

how  paid  for 386,  387 

term  of,  principles  determining 386,  387 

Gutters,  depth  of,  how  determined  200 

for  asphalt  pavement,  how  laid . .   236,  401 

material  for 286 

for  broken-stone  pavement 347 

forms  of „ 481 

how  laid 480 

materials  for 480 

Hardness  and  specific  gravity  of  paving-brick 276 

of  asphaltic  cement,  how  tested 223,  224 

of  paving-brick,  how  tested  . .   262 

Mohs'  scale  for 262 

value  of  tests  for 270 

Heading-stones,  dimensions  of 395 

how  set 395 

Highway  Act,  first,  in  England 4 

Holborn,  pavements  of 5 

Hornblende   15 

Hornblende  granite 1H 

Hornblende,  biotite  granite 18 

Hudson  River  blu'estone,  composition  of 30 

description  of 2!) 

location  of 2!) 

Hydraulic  limestone,  composition  of 90 

definition  of 90 

Illuminating-gas,  effect  of,  on  asphalt  pavements 239 

Indian  Territory  asphalt 76 

Instructions  to  bidders 382 

Iron  macadam  pavements 141 

Iron  pavements 138,  139 


514  INDEX. 

PAGR 

Italy,  pavements  of U 

Jasperite  pavement 140 

Jerusalem,  streets  of 3 

Jetley  pavement 145 

Joint-filling 197,  208 

for  brick  pavement  284,  286,  4ia 

in  Philadelphia , 291 

in  St.  Louis 290 

for  Medina  sandstone  pavement 409 

for  wood; 294,  295,  299,  301,  303,  308,  318,  319- 

Joints  in  pavement,  tar  and  gravel  first  used 7 

in  New  York  City 10 

Joints  in  street-car  tracks,  effect  of,  on  traction 451,  452 

how  made 451 

number  of  special,  in  Brooklyn 452. 

in  Chicago 452 

Kaolin,  analysis  of 80,  86 

characteristics  of 80 

chemical  formula  for > 8u- 

fluxes  for 81 

formation  of 80,  86. 

Kentucky  asphalt 72 

Kyanizing 323 

Life  of  asphalt  pavements 156 

in  London 243, 

Belgian-block  pavements 156 

brick  pavements 156 

in  Holland 258 

granite  pavements 156 

Medina  sandstone  pavements 207 

pavements  in  European  cities 156 

wood  pavements  in  Chicago 313 

in  London 296 

in  Omaha 311 

in  Paris 303 

in  Quebec 304 

Lime,  definition  of 96 

analysis  of 38 

Limestone,  analysis  of .36,  37,  38,  39 

Bedford  oolitic,  analysis  of 37 

description  of 30 

effect  of  heat  on 37 

strength  of 37 

dolomite , 35 

for  macadam  pavements 341 


INDEX.  515 


Limestone,  formation  of 34 

hydraulic,  analysis  of 30 

definition  of 36,  96 

marble,  definition  of 36 

oolitic,  formation  of 35 

»   strength  of ...     39 

Trenton,  analysis  of 38 

location  of 37 

uses  of 37 

Liquid  asphalt,  how  used 401 

properties  of 401 

Lithuania,  pavements  of 7 

Liverpool,  granite  blocks  first  used  in 7 

London,  early  wood  pavements  of 6 

streets  of 5 

Macadam  pavement,  see  Broken-stone  pavement. 

roads 350 

amount  built  in  New  Jersey 352 

appropriation  for,  in  Massachusetts 350 

in  New  York 352 

character  of  stone  for '. . .   357 

cost  of  construction  of,  estimated 363 

in  Massachusetts 362 

in  New  Jersey 362 

drainage,  necessity  for 353 

rules  of  Mass.  Highway  Commissioners  for. 354,  355 

how  paid  for,  in  Massachusetts 351 

in  New  Jersey 351 

in  New  York 352 

maintenance  of :  cost  of,  in  England 370 

in  France 370 

in  Europe 371 

methods  of 369 

quantity  of  material  used  in 369,  370 

quantity  of  material  for 361 

questions  governing  construction  of 353 

ruts  in 371 

specifications  for :  New  Jersey  366 

New  York 364 

Owen's 368 

sprinkling 372 

stone  for,  in  Massachusetts 35S 

abrasion  test  of 359 

description  of  test  of 359 

machine  for  test  of  . .  .  359 


516  INDEX. 

PAGE 

Macadam  roads,  stone  for,  in  Massachusetts,  size  of 35& 

width  and  thickness  of,  how  determined 35ft 

Macadam's  theory  of 331 

standard  for,  in  Mass. . . 356,  35T 

N.J... ..*.... 866,  357 
Queen's  Co.,  L.  I.  357 

Magnesia,  maximum  amount  in  Portland  cement 99' 

Maintenance:  asphalt  pavements,  Buffalo  method 245 

Cincinnati  method ...   245 

Cost  of,  in  Buffalo 246,  247 

Cincinnati 246,  247 

European  cities 248 

Omaha 246,  247 

Rochester 24$ 

Washington. 246,  247 

Omaha  method 244 

Washington  method 246- 

how  paid  for 386,  387 

Macadam  roads 370 

period  of 384.  386 

conditions  governing 385 

wood  pavements 297,   300 

Maltha,  analysis  of 63 

as  a  flux 223 

definition  of 43- 

deposits  of 62 

description  of 62 

how  obtained  62 

Marble 06- 

Material,  quantity  of,  for  asphalt  pavements 489,  490,  491 

Belgian  pavements 187 

brick  pavements  292 

cobblestone  pavements 184 

granite  pavements 206 

macadam  streets  and  roads. 361 ,  363 

maintaining  macadam  streets  and  roads . . .   .369,  370 

Medina  sandstone,  composition  of 32 

description  of 31 

location  of 31 

pavements,  cost  of,  in  Cleveland » 208; 

Rochester 208; 

description  of  blocks  for 201 

dimension  of  blocks  for 207 

how  laid  in  Cleveland 20T 

Rochester 2.08 


!  INDEX.  517 

PAOK 

Medina  sandstone  pavements,  joint-filler  for 208 

Medina  sandstone  pavement,  specifications  for  : 

classes  of  blocks 406- 

covering  for 410 

description  of  blocks 406 

how  laid 408 

ramming 408 

joint-filling 409 

how  applied 410 

Mexican  asphalt 68 

Mexico  City,  pavements  of 8 

Mica,  description  of 16 

varieties  of 16 

Montana  asphalt 77 

Mortar,  action  of  frost  on 113: 

composition  of 109 

cost  of 472 

definition  of 10» 

in  salt  water Ill 

strength  of Ill,   112 

material  in 472 

mixed  with  salt  water 112 

strength  of 114 

rule  for  amount  of  salt  in 1 13 

time  of  use  after  mixing 118,   lift 

unit  of  measurement  of 110 

volume  of 110,  12$ 

Mud  clays 84 

Muscovite  biotite  granite 18 

Muscovite  granite 18 

Murphy  grout 197 

Natural  gas  a  bitumen 44 

Napthalene,  value  of,  in  creosote 326 

New  Orleans,  early  pavements  of 12 

New  York,  concrete  base  for  pavements  first  used  in 10- 

early  pavements  of ft 

first  asphalt  pavement  in 215 

first  cobblestone  pavement  in 8 

mortality  of 166 

Noiseless  manhole-covers 249 

Noiseless  stone  pavement 144 

Notice  to  bidders 390 

Oolitic  limestone / 35,  36 

Palenque,  Mexico,  pavements  of S 

Paris,  first  asphalt  pavement  of & 


518  INDEX. 

PAGJS 

Paris,  first  pavement  of 4,  7 

streets  of 7 

Pavements,  annual  cost  of 171,  172 

in  New  York 136 

artificial  blocks  for 141 

asphalt 211 

accidents  on 161,  162 

first  in  New  York -215 

first  in  Paris 8 

first  in  United  States  215 

in  Cairo... 143 

slipperiness  of 161 

•  asphalt  block 255 

asphaltina 253 

assessments  for,  how  paid 137 

Belgian 9,  184 

best  for  steep  grades  483 

brick 258 

broken  stone 329 

ceramite  blocks  for 143 

chert 142 

choice  of 136 

coal-tar 211,  212 

cobblestone. ... 1 82 

combination,  wood  and  asphalt 144 

construction  of,  early . . . .  178 

crown  of,  formula  for  laying  out 2(  2 

on  side-hill  streets 201 

principles  for  determining 200,  201 

table  for 202 

definition  of 135 

derivation  of  word . . . . , 135 

early,  of  Albany ; 13 

Baltimore 11 

Boston 10 

Chicago 11 

Cleveland  12 

Europe  179 

New  Orleans 12 

Philadelphia 11 

San  Francisco 12 

St.  Louis 13 

early  wood,  of  London 6 

estimated  value  of,  in  New  York. 136 

experimental  wood 140 


INDEX.  519 

PAGE 

Pavements,  favorableness  to  travel,  discussion  of 164 

examples,  of  in  Brooklyn 164 

London 165 

Poughkeepsie 164 

for  country  roads 169 

for  residence  streets 168 

glass 141 

granite 188 

accidents  on 161,  162 

slipperiness  of 161 

grass 140 

Guidet ft 

increase  of,  in  last  decade  : 

in  Boston 173: 

in  Brooklyn 173- 

in  Buffalo 173 

in  Chicago 173 

in  New  York 173 

in  Philadelphia 173 

in  St.  Louis 173 

in  Washington  173 

influence  of 1 35 

iron  138 

iron  in  Berlin 139 

iron  macadam 141 

jasperite 140 

jetley 145 

joint  filling  for,  see  Brick,  Stone,  and  Wood  pavements. 

material  used  in 137 

Medina  sandstone 207 

method  of  payment  for 138 

mileage  of,  in  New  York 136 

noiseless  stone 144 

of  Catania,  Italy 179 

of  Cordova,  Spain 5 

of  Holborn 5 

of  Italy 6 

of  Lithuania T 

of  Mexico  City & 

of  Philadelphia 14& 

of  Rome 4,  5 

of  West  Indies    7 

openings  in,  how  prevented  in  Rochester 175 

how  repaired 1 76 

number  of,  in  Boston 17& 


520  INDEX. 


Pavements,  openings  in,  number  of,  in  Brooklyn 175 

New  York 175 

purposes  of 174 

origin  of 177 

Pelletier  blocks 142 

Portland  cement 142 

properties  of  an  ideal 147 

cheapness 147 

durability 147 

durability  influenced  by  what 147 

easily  cleaned 150 

easily  maintained 1 51 

favorableness  to  travel 152 

non-slippery 151 

resistance  to  traffic 151 

sanitariness 152 

relative  values  of 167 

renewal  of 170 

repairs  to  cobblestone \ 164 

granite-block 163 

macadam 163 

sanitariness  of 166 

conditions  of 166 

examples  of,  in  New  York 166 

how  accomplished  in  London 165 

Scrimshaw... 211 

selection  of  material  for 146 

shell 142 

specification  Belgian 186 

steel-rails  in « 143 

study  of  standard 153 

annual  cost  of 155 

durability  of 154 

easily  cleaned 156 

economic  life  of 1 55 

estimated  life  of,  in  American  cities 156 

first  cost  of 154 

kinds  of 153 

life  of,  in  European  cities 156 

resistance  to  traffic 156,  157,  158,  159 

tar  macadam • 140 

value  of 136 

wood 293 

accidents  on 161,  162 

slipperiness  of 161 


INDEX.  521 

PAGE 

Pavements,  wood  pulp 144 

Pavement  between  street-car  tracks,  how  paid  for 425-428 

how  laid 454 

Paving-brick,  analysis  of 260 

crushing  clay  for 90 

density  of 264 

first  used 89 

form  of 280 

hardness  of,  how  tested 262 

homogeneity  of 263 

porosity  of 264 

production  and  value  of 89 

relative  values  of 277,  278 

requirements  of 261 

size  of 279,  280,  281 

specifications  for 281,  289 

strength 263 

tests  for  abrasion 266 

absorption 270 

cross- breaking 273 

crushing 275 

hardness 262 

in  Columbus,  Ohio 279 

toughness  of 262 

uniformity  of 263 

wear  of 265,  266,  267 

Paving-brick,  manufacture  of:  annealing,  importance  of 94 

time  required  for 94 

burning,  beginning  of  vitrification 93 

changes  of  clay  in 93 

fuel  for 94 

importance  of , 93 

kiln  for 93 

pugging 90 

temperature  for 94 

time  required  for 94 

drying 92 

screening  clay  for 90 

machine  for 91 

capacity  of 91 

moulding 91 

repressing 92 

sorting,  proportion  of  different  grades 95 

Paving-cement,  amount  per  square  yard  of  pavement 199,  205,  292 

composition  of  197,  319 


522  INDEX. 

PAGE 

Paxing-cement,  temperature  of 205,  319 

Paving  material,  report  of  Philadelphia  committee  on 180 

St.  Louis  experiments  on 155 

Pelletier  blocks 142 

Penalty  for  failure  to  complete  contracts 384 

Pennsylvania  bluestone 3O 

Petrolene 51 

formula  for 52,  54 

Petroleum,  asphalt  from  64 

amount  of 65 

California 44,  50 

Eastern 50 

oxidation  of , 43- 

requirements  of.. 398 

residuum,  amount  used  with  Trinidad  asphalt 223- 

as  a  flux 221 

Philadelphia,  early  pavements  of 11 

streets  of & 

Pitch,  derivation  of  word 40 

Pitch  Lake,  Wall  and  Sawkins,  description  of 48 

Pittsburg  flux  223- 

Plans,  how  much  to  be  shown  on 378 

object  of 37(> 

should  be  part  of  contract 389* 

should  be  signed  by  contractor 389 

should  show  amount  of  work  to  be  done 379,  389- 

should  supplement  specifications 376 

when  to  be  prepared  by  contractor 378 

Plasticity  of  clay 82,  84,  87 

Pompeii,  streets  of 7 

Porphyry,  analysis  of 80,  86 

description  of 20 

formation  of 20 

Portland  cement 97 

for  joint-filling 197,  291,  301 

pavements 141 

Potsdam  sandstone 321 

Pottery,  early  use  of 88 

Proposals,  conditions  of 391 

Pyroxene 16 

Quartz  14 

Quartzite 15 

Kails  of  street-car  tracks,  Boston 436 

"      subway 437 

early  form  of 430,  431 


INDEX.  523 

PAGE 

Rails  of  street-car  tracks,  girder,  centre-bearing 433 

life  of 450 

renewable  heads 432,  433 

side-bearing 434 

tee  437 

Trilby 435 

Trilby  modified 435 

Railway  ties,  chemical  treatment  of 324,  325 

Refractoriness  of  clay 84,  85,  87 

Repairs,  see  Maintenance. 

Repairs  to  coal-tar  pavements,  cost  of 212,  213 

Report  on  rock-asphalt  pavements  of  London 243 

Roads,  asphalt,  in  California 12 

charcoal 293 

first,  in  France 4 

Rome 2 

Spain 4 

stone 2 

macadam  350 

Mexican 3 

officials,  first,  in  France 3 

Peruvian 3 

Roman 177 

Russian 4 

Roadway  of  street,  how  determined 460 

width  of 460,  461 

Rock,  definition  of 14 

stratified 14 

study  of 16 

unstratified 14 

Rock-asphalt,  California 66 

European 67 

Indian  Territory , 76 

Kentucky 72 

Texas 73 

Rock-asphalt  pavement,  binder  not  used  with 243 

bitumen  in 242 

Buffalo 241 

composition  of 241 

how  laid 242 

London  report  on 243 

specifications  for,  in  St.  Louis 242 

temperature  of,  when  laid 243 

Hollers,  size  of,  for  asphalt  pavements 234 


524:  INDEX. 

PAQK 

Rollers,  size  of,  for  broken-stone  pavements 338,  348,  349 

Rolling,  amount  for  asphalt 235 

macadam 338,  341,  342,  34a 

depends  upon  what 340 

standard  for 342 

Rome,  pavements  of 4,  5 

Rumbling  of  brick  pavements 285 

Russ  blocks  in  New  York 9- 

Ruts  in  macadam  roads , 371 

Sample  to  be  submitted 390,  392 

Sand,  amount  of,  in  asphalt  pavement 489 

formation  of 27 

size  of,  in  asphalt  pavement 227 

voids  in 122 

Sandstone,  Berea 32: 

Colorado 33 

color  caused  by 28 

description  of 28 

formation  of 28 

Hudson  River , 29 

kinds  of 29* 

Medina 31 

Potsdam 32 

strength  of 33 

San  Francisco,  pavements  of 12 

Scrimshaw  pavement 211 

Set,  initial 107 

final , 107 

Shale 83 

analysis  of 85 

Shale  brick 85 

Shell  pavement 142 

Sidewalks,  brick 477 

cement  478- 

specifications  for 478,  479 

in  business  sections 474 

material  for 475 

slope  of 474 

space  for,  how  treated 462 

stone. 475 

specifications  for 479 

width  of ; 462,  474 

Sioux  Falls  stone 21 

Slate 83 

Specific  gravity  of  paving-brick 275,  27& 


INDEX.  525 

PAGE 

Specifications,  Belgian  blocks 185 

Belgian-block  pavement 186,  18T 

Specification,    acceptance  of  work 41$ 

asphalt  pavement 39T 

asphaltina  cement , 254 

asphaltena,  wearing  surface 254 

asplialt-block  pavement 413 

Belgian  block 185 

pavement  186 

brick 410 

in  Philadelphia 291 

in  St.  Louis 289 

brick  pavement 410 

in  Philadelphia 291 

in  St.  Louis 290 

broken-stone  pavement,  Boston 348 

Brooklyn 349- 

Providence 347 

catch-basins  to  be  adjusted . .  41  .> 

cement 396 

curbing 471 

gutter 471 

sidewalks 478,  470 

character  of  work 391 

coal-tar  pavement 213 

competition  allowed 377 

concise,  to  be 376 

concrete 396 

contractor,  meaning  of  word 416 

creosoting 327 

in  Indianapolis 318 

in  London   299 

railway  ties 323 

cross-walks 394 

curbing 394,  468,  469,  471 

damages  for  non-completion 416 

provisions  for 415 

embankment,  how  made 393 

slopes  in 39IJ 

enforcement  of 378 

excavation,  how  made 3SJ3 

slopes  in 393 

extra  work,  provision  for 381 

granite  blocks 190 

pavement 403 


526  INDEX 

PAGE 

Specification,  guarantee 417 

hard- wood  pavement  in  London 298 

beading-stones , 395 

injured  material,  how  replaced. 415 

injuries,  provisions  for 415 

macadam  roads,  New  Jersey 366 

NewYork 366 

Owen's , 368 

maintenance 384,  418 

manholes  to  be  adjusted 415 

Medina  sandstone  blocks 207 

pavement 406 

Nicholson  pavement 308 

object  of 376 

openings  to  be  restored 419 

ordinances  to  be  obeyed 417 

pavement,  maintenance  of 418 

payments 420 

plain,  to  be 377 

roadbed,  how  prepared 394 

rock-asphalt  pavements  in  St.  Louis 242 

rubbish,  removal  of 393 

sewer-laying  permitted 392 

sidewalks,  cement 478,  479 

how  graded 393 

stone 479 

soft-wood  pavements  of  London 299 

street  to  be  cleaned  up 415 

water-pipe  laying  permitted ^ 392 

wood  pavements  of  Indianapolis 318,  319 

work,  delay  of 417 

how  protected 416 

how  suspended 416 

partial  completion  of 416 

time  of 416 

workmen  to  be  discharged 41 6 

Sprinkling  broken-stone  pavements 346 

macadam  roads 372 

Steel  rails  in  paved  road 143 

St.  Louis,  early  pavements  of 13 

Stone  blocks,  size  of 191,  192 

cementitious  properties  of 344 

tests  for 344 

value  of 360 

machine  for  testing 345 


INDEX.  527 

PAGE 

Stone  coefficient  of  wear  of 360 

for  macadam  roads 357 

Stone  sidewalks,  foundations  for 477 

size  of  stone  in. 475,  476,  480 

specifications  for 479 

Strand,  London,  ordered  paved 5 

Street-cars,  weight  of 421 

Street-car  tracks,  amount  of,  in  American  and  European  cities 458 

in  United  States 458 

construction  of  :    cost  of  creosoted  ties  in 456 

cost  of,  in  Minneapolis 449 

difference  in  opinion  concerning 422 

how  decided  upon 423,  450 

ideal 422 

improved  forms  in  Buffalo 438,  430 

in  Brooklyn 440 

in  Cincinnati 445 

in  Detroit 444 

in  Dublin 449 

in  Minneapolis 448 

in  Rochester  . .  .446,  447 
in  Sioux  City. .  .440,  442 
in  Third  Ave.,  N.Y.  443 

in  Toronto .    .  440 

in  macadam  roads . .  456 

recommended  for  asphalt  pavement 453 

for  brick  pavement 455 

for  granite  pavement 453 

early  rails  of 430,  431 

improved  form  of  rails 432,  433,  434,  435,  436 

filling  between  flanges  of 455 

joints  in,  how  made 451,  452 

location  of  Beacon  street,  Boston 429 

Canal  street,  New  Orleans 429 

city  streets 428 

country  roads 429 

pavement  in,  how  laid ,... 454 

Glasgow  method 458 

in  old  construction 457 

"»  how  paid  for  in  Amsterdam 427 

Baltimore 424 

Berlin 428 

Brooklin 424 

Buffalo , 424 

Chicago 424 


528  INDEX. 

PAGE, 

Street-car  tracks,  pavement  in,  how  paid  for  in  Detroit 424 

Dorchester,  Mass 423 

Great  Britain 427 

Hamburg 428 

Indianapolis 424 

New  York 425 

Philadelphia 42") 

Rochester 42-"> 

St.  Louis 420 

Toronto 4',>6- 

Vienna 428 

Washington 42? 

traction  on 451 

Street  railways,  first  operated  in  Boston 429 

Glasgow 430 

London 430 

New  York 42& 

Philadelphia 429 

Streets,  courtyards  in 460,  462 

Boston 10 

Genoa 3 

Jerusalem 3 

London 5 

New  York 9 

Paris 7 

Philadelphia 9 

Pompeii „ 7 

Thebes 3 

space  of,  how  divided 4<  1 

width  between  curbs,  how  determined 460 

treated 460,  461 

width  of 459- 

Syenite 19- 

Syrian  asphalt 76 

Tar-and-gravel  joints,  construction  of 199- 

first  used T 

in  New  York 10- 

Tar  macadam  pavement  140 

Telford's  roads 330- 

Temperature  for  laying  asphalt  pavement 237 

Tensile  strength,  natural  cement 101 

Portland  cement 10T 

requirements  for 109* 

specifications  for 108 

Texas  asphalt 7a 


INDEX.  529 

PAGE; 

Thebes,  streets  of 3 

Timber,  see  Wood. 

Tires,  width  of 373,  374,  375 

effect  of 158 

in  foreign  countries 375 

New  Jersey 37.0 

laws  concerning,  New  York 374 

Michigan 373 

Ohio 374 

Rhode  Island 373 

Traction,  experiments  on,  by  Department  of  Agriculture 157 

Studebaker  Brothers 158 

general  table  for 159 

Prof.  Haupt's  table  for 158 

Society  of  Arts'  table  for 1 59 

Traffic  affected  by  character  of  pavement 149 

how  well  cleaned 149 

state  of  repair 149 

street-car  tracks 149 

width  of  roadway 148 

in  American  Cities  » 148 

European      "      148 

Tramway  streets  in  Italy 6 

Philadelphia 181 

Trap-rock  20 

analysis  of 26,  27 

for  broken-stone  pavements 338,  339 

Tresaguet's  roads 329 

Trinidad  Lake,  description  of 57,  58,  59 

location  of 57 

size  of 58 

Trinidad  Lake  asphalt,  analysis  of 54,  60,  61,  495,  496 

bitumen  in 228 

mining  of 58 

refining    60,  61 

Turkey  asphalt  78 

Unbalanced  bids 388 

how  prevented  in  Jersey  City 389 

Values,  relative,  of  paving-brick 277,  278 

Vitrification,  beginning  of,  in  burning  brick 93 

definition  of 86 

Vitrified  brick,  see  Paving-brick. 

clay  to  produce t 87 

definition  of : 86 

test  for..  87 


530  INDEX. 

PACK 

Voids,  broken-stone 120,  124,  343 

gravel 124 

sand 122,  124 

stone  and  gravel  mixed 124 

Wax  tailings • 212 

West  Indies,  pavements  in 7 

Wood,  chemical  treatment  of  :  best  method 328 

•Burnettizing 323 

creosoting 323 

early  methods  of 323 

experiments  with  railway  ties 325 

kyanizing 323 

method  for  railway  ties 323 

operations  of 326 

railway  ties  in  Germany,  cost  and  durability  325 

specificationsjor 299,  318,  327 

Wellhouse  process  modified 324 

when  necessary  in  pavements 322 

zinc  creosote  process 325 

tannin  process 324 

Wood  and  asphalt  pavement 145 

Wood  as  a  paving  material 312,  328 

Wood  pavements,  Australia,  cost  of 321 

description  of 320 

durability  of 321 

material  for 320 

wear  of 320 

Australian,  in  New  York , 321 

Berlin 302 

Boston 306,  308 

buckling  of 316,  317 

cedar-block 310 

quantity  of,  in  leading  cities 315 

Chicago,  foundation  for 310 

how  laid 311 

material  for 310 

cypress-block 310 

Dublin 302 

early,  of  Russia 293 

experimental 140 

Edinburgh 302 

Glasgow 301,  302 

gravel  and  concrete  foundations  compared 300 

Indianapolis,  cost  of 318 

description  of 317 


INDEX.  531 

PAG": 

Wood  pavements,  Indianapolis,  material  of 317 

specifications  for 318 

Ipswich,  England 300 

Ker  system 307 

London 6 

Australian,  in  Paddington 300 

specification  for 298 

statistics  of 298 

Strand  district 299 

•Gary  system 294 

concrete  base,  first  used  for 294 

•cost  of  297 

cost  of  repairs  to 297 

first  laid 293 

Benson's  system 295 

improved  system 294 

life  of 291) 

method  of  laying 294,  295 

report  on 296 

•wear  of 296 

Miller  system,  cost  of 310 

description  of 309 

life  of 310 

Montreal 304 

New  York 806,  308 

Nicholson  system,  cost  of 309 

life  of 309 

specifications  for t . . .  308 

Oakland,  California 316 

Paris,  amount  of 804 

cost  of 304 

description  of 303 

life  of 303 

material  for 303 

wear  of 303 

Philadelphia,  conclusions  concerning 306 

cost  of 305 

durability  of 306 

material  for 306 

report  on 305 

Quebec,  cost  of 305 

description  of 304 

life  of...   304 

method  of  laying 304 

San  Antonio .  316 


532  INDEX. 

PAGE 

Wood  pavements,  St.  Louis 308 

Washington,  amount  in  1871 307 

cost  of 307 

durability  of 307 

Wooden  roads,  early . 293 

in  Michigan 293 

Wood  pulp  pavements 144 


INDEX    TO    ADVERTISEMENTS. 


PAGE 

Barber  Asphalt  Paving  Company,  The I 

Commercial  Wood  and  Cement  Company 4 

Copley  Cement  Company,  The 5 

Cranford  Company 3 

Lawrence  Cement  Company,  The 2 

New  York  and  Bermudez  Company 2 

Ransome  &  Smith  Company 4 

Wilson  &  Baillie  Manufacturing  Company,  The 5 

Wiley  &  Sons,  John 4 


OF   THE 

UNIVERSITY 


ASPHALT  PAVEMENTS. 


FOR   INFORMATION,    CATALOGUES, 


THE  BftRBER  ASPHALT  PAVING  COMPANY 


11    BROADWAY,    NEW  YORK, 


OR   ANY   OF  THE   BRANCH    OFFICES. 
1 


15,000,000    BARRELS 

HOFFMAN"  Cement 


Have  Been  Used  on  Important  Work 
THROUGHOUT   THE    UNITED   STATES. 

NO  OTHEE  CEMENT  COMPANY  CAN  SHOW  SUCH  A  EECOED 


IHEUWiOMUICL 

Established  1853. 
E.  R.  ACKERMAN,  Pres....Assoc.  Am.  Soc.  C.  E. 

SALES  OFFICE:  No,  1  BROADWAY,  NEW  YORK. 


NEW  YORK  AND  BERMDDEZ  COMPANY 


For  particulars  address  General  Office, 

BOWLING  GREEN  BUILDING, 

2 


5 

Owners  of  the  largest  ASP  HAL  T 
LAKE  in  the  WORLD,  situated 
in  the  State  of  Bermudez, 
Republic  of  Venezuela,  South 
America. 

Bermudez  Lake  Asphalt  is  the 
PUREST  and  is  unexcelled 
by  any  other  for 

STREET  PAVING, 
RESERVOIR  LINING, 
WATERPROOFING, 
ROOFING,  etc, 

NEW  YORK. 


J.  P.  CRANFORD,  President 

F.  L.  CRANFORD,  ^ice-President. 

W.  V.  CRANFORD,  Secretary  and  Treasurer. 


CRANFORD   COMPANY, 


Asphalt   Pavements, 


GENERAL    CONTRACTORS, 


Mechanics   Bank   Building^ 


215  MONTAGUE   STREET, 


Telephone  1180  Bed.ord.  BROOKLYN,     NEW    YORK. 


Works:   524  St.  Harks  Ave. 
3 


"iron  oar  Portland  Cements 

Manufactured  by 

GLENS  FALLS  PORTLAND 
CEMENT  CO. 

Sole  Selling  Agent: 

'Commercial  Wood 
and  Cement  Co. 

156  FIFTH  A7E.,  NEW  Y02Z. 

From  James  D.   Scfiuyler,    Consulting    Hydratilic  Engineer, 
JMS  Angeles,    California. 

"  MY  DEAR  SIR  : 

"  Everybody  is  simply  astonished  at  the  performance  of  the  mixers. 
They  are  surely  the  greatest  machines  for  the  purpose  ever  invented. 

"  I  have  used  all  kinds  of  mixers,  but  these  are  so  far  superior  to  any 
other  device  with  which  I  am  familiar  that  I  should  never  think  of  using 
any  other.  "  Sincerely  yours, 

(Signed)     "  JAS.   D.  SCHUYLER,  M.A.S.C.E." 

Mr.  Schuyler  employed  six  of  our  drum  mixers  on  the  Portland  water- 
works, Portland,  Oregon. 

RANSOME  CONCRETE-MIXERS. 

RANSOME  &  SMITH  CO., 

17  and   19    NINTH    ST.,   BROOKLYN,   N.  Y. 


From  Professor  S.  S.  Netvberr'/'s  report  on  Annual  Meeting  of  the  Asso- 
ciation of  German  Cement  Manufact\irers,  Eng.  News,  Feb.  25,  1897. 

"  In  building  the  Munderkingen  Bridge,  a  concrete  of  I  cement,  2)4 
sand,  and  5  gravel,  mixed  in  a  drum  mixer,  gave  a  compressive  strength 
of  340  tons  to  square  foot,  whilst  the  same  mixture,  in  same  job,  mixed  by 
hand,  gave  a  compressive  strength  of  only  184  tons  to  square  foot." 

Inspection  of  the  Materials  and  Workmanship 

Employed  in  Construction. 

A  reference  book  for  the  use  of  inspectors,  superintendents,  and  others  engaged  in  the 
construction  of  public  and  private  works.  Containing  a  collection  of  memoranda  pertaining 
to  the  duty  of  inspectors;  quality  and  defects  of  materials;  requisites  for  good  construction; 
methods  of  slighting  work;  etc.,  etc. 

By  AUSTIN  T.  BYRNE,  Civil  Engineer,  author  of  "  Highway  Construction." 
xvi-f  540  pages.      12010.     Cloth,  $3.00. 

Order  through  your  bookseller,  or  copies  'will  be  forwarded,  postpaid,  by  the  publishers  on 
the  receipt  of  the  retail  price. 

NEW  YORK:  LONDON: 

JOHN   WILEY  &  SONS.  CHAPMAN  &  HALL,   LIMITED. 


T.  HENRY  DUMARY,  President. 
S,  OLIN  JOHNSON,  Vice- President. 


E.  H.  BAILLIE,  Secretary. 

F.  B.  JOHNSON,  Treasurer. 


The  Wilson  &  Baillie  Manufacturing  Co. 

Main  Office  and  Factory,  85-93  Ninth  Street,  Brooklyn,  N.  Y. 

MANUFACTURERS  OF 

ARTIFICIAL    STONE. 

For  Sidewalks,  Driveways,  Copings,  Steps,  Bailroad  Depot  Flat  form:,  Flooring  for  Warehouses  and 
Apartment  Houses,  Water-tight  Cellar  Floors,  and  Improved  Stable  Floors. 

Kosmocrete  Steel-Bound  Curb, 

"  Wainwright's   Patents." 

The  Steel-Bound  Curb  is  su- 
perior to  any  natural  stone. 

Laid  in  ten-foot  lengths,  with 
invisible  joints,  with  concrete 
foundations,  is  never  out  of  line. 

Galvanized  steel  edges  cannot 
rust  or  break. 

It  is  the  most  beautiful  and 
durable  curb  laid,  and  with  gut- 
ter combined  is  the  ideal  for  as- 
phalt, brick,  or  macadam  streets. 

Heavy  Concrete  Construction 

A  Special  Feature  of  our  Business. 


A  natural  cement 
resembling  a  Port- 
land in  color  and 
texture. 


ROSENDALE 
CEMENT 


The  most  eco- 
nomical cement  on 
the  market  on  ac- 
count of  its  great 
sand-carrying  ca- 
pacity. 


MANUFACTURED    BY 


THE    COPLAY    CEMENT    CO. 

The  favorite  brand  of  natural  hydraulic  cement  for  the 
concrete  foundation  of  street  pavements. 

Nearly  half  a  million  barrels  have  been  used  by  the  Asphalt 
Companies  in  the  Boroughs  of  Manhattan,  Brooklyn,  and  Queens, 
N.  Y.  City;  Syracuse,  1Y.  Y.,  Utica,  N.  Y.,  Camden,  N.  J.,  and 
Newark,  N.  J. 

For  prices,  tests,  etc.,  apply  to  the  sole  selling  agent, 

Commercial   Wood   &   Cement  Co., 

156  Fifth  Avenue,  New  York. 


SHORT-TITLE    CATALOGUE 

OF  THE 

PUBLICATIONS 

OF 

JOHN   WILEY   &    SONS, 

NEW    YORK, 
LONDON:    CHAPMAX   &    HALL,   LIMITED. 


ARRANGED  UNDER  SUBJECTS. 

Ojt-  -'   'I  I          '  I         •'•?'*   '• 

Descriptive  circulars  sent  on  application. 

Books  marked  with  an  asterisk  are  sold  at  net  prices  only. 
All  books  are  bound  in  cloth  unless  otherwise  stated. 


AGRICULTURE. 

CATTLE  FEEDING — DAIRY  PRACTICE — DISEASES  OF  ANIMALS — 
GARDENING,  HORTICULTURE,  ETC. 

Arinsby's  Manual  of  Cattle  Feeding 12mo,  $1  75  - 

Budd  and  Hausen,  American  Horticulture  Manual ..  (In  press. ) 

Downing's  Fruit  and  Fruit  Trees 8vo,  5  00 

Grotenfelt's  The  Principles  of  Modern  Dairy  Practice.     ("Woll.) 

12mo,  2  00 

Kemp's  Landscape  Gardening 12mo,  2  50 

Mayuard's  Landscape  Gardening 12mo,  1  50 

Steel's  Treatise  on  the  Diseases  of  the  Dog 8vo,  3  50 

"      Treatise  on  the  Diseases  of  the  Ox.  .(LJ.:'.0.'u>.' 8vo,  6  00 

Stockbridge's  Rocks  and  Soils 8vo,  2  50 

Woll's  Handbook  for  Farmers  and  Dairymen 12mo,  1  50 

ARCHITECTURE. 

BUILDING — CARPENTRY— STAIRS — VENTILATION — LAW,  ETC. 

Birkmire's  American  Theatres— Planning  and  Construction,  8vo  3  00 

"        Architectural  Iron  and  Steel 8vo,  3  50 

"        Compound  Riveted  Girders 8vo,  2  00 

"        Skeleton  Construction  in  Buildings 8vo,  3  Oft 

1 


Birkmire's  Planning  and  Construction  of  High  Office  Buildings. 

8vo,  18,0 

Briggs'  Modern  Am.  School  Building 8vo,  4  00 

Carpenter's  Heating  and  Ventilating  of  Buildings 8vo,  3  00 

Freitag's  Architectural  Engineering 8vo,  2  50 

The  Fireproofing  of  Steel  Buildings 8vo,  2  50 

Gerhard's  Sanitary  House  Inspection 16mo,  1  00 

Theatre  Fires  and  Panics 12mo,  1  50 

Hatfleld's  American  House  Carpenter 8vo,  5  00 

Holly's  Carpenter  and  Joiner 18mo,  75 

Kidder's  Architect  and  Builder's  Pocket-book. .  .16mo,  morocco,  4  00 

Merrill's  Stones  for  Building  and  Decoration 8vo,  5  00 

Monckton's  Stair  Building—Wood,  Iron,  and  Stone 4to,  4  00 

Wait's  Engineering  and  Architectural  Jurisprudence 8vo,  6  00 

Sheep,  6  50 

Worcester's  Small  Hospitals — Establishment  and  Maintenance, 
including  Atkinson's  Suggestions  for  Hospital  Archi- 
tecture  12mo,  125 

*  World's  Columbian  Exposition  of  1893 Large  4to,  1  00 

ARMY,  NAVY,  Etc. 

MILITARY  ENGINEERING— ORDNANCE — LAW,  ETC. 

*  Bruff' s  Ordnance  and  Gunnery 8vo,  6  00 

Chase's  Screw  Propellers 8vo,  3  00 

Cronkhite's  Gunnery  for  Non-com.  Officers 32mo,  morocco,  2  00 

*  Davis's  Treatise  on  Military  Law 8vo,  7  00 

Sheep,  7  50 

*  "      Elements  of  Law 8vo,  2  50 

De  Brack's  Cavalry  Outpost  Duties.     (Carr.). . .  ,32mo,  morocco,  2  00 

Dietz's  Soldier's  First  Aid 16mo,  morocco,  1  25 

*  Dredge's  Modern  French  Artillery Large  4to,  half  morocco,  15  00 

*  "         Record  of  the  Transportation   Exhibits    Building, 

World's  Columbian  Exposition  of  1893.. 4to,  half  morocco,  5  00 

Durand's  Resistance  and  Propulsion  of  Ships 8vo,  5  00 

*  Fiebeger's    Field   Fortification,    including   Military   Bridges, 

Demolitions,  Encampments  and  Communications. 

Large  12mo, 

Dyer's  Light  Artillery 12mo,  3  00 


Hoff's  Naval  Tactics  ....................................  8vo,  $1  50 

*  Ingulls's  Ballistic  Tables  ...............    ................  8vo.  1  50 

Handbook  of  Problems  in  Direct  Fire  ...........  8vo,  4  00 

Mahaii's  Permanent  Fortifications.  (Mercur.  ).  8  vo,  half  morocco,  7  50 

*  Mercur's  Attack  of  Fortified  Places  ...................  12mo,  2  00 

*  "        Elements  of  the  Art  of  War  ...................  8vo,  4  00 

Metcalfe's  Ordnance  and  Gunnery  ...........  12mo,  with  Atlas,  5  00 

Murray's  A  Manual  for  Courts-Martial  ........  16mo,  morocco,  1  50 

"        Infantry  Drill  Regulations  adapted  to  the  Springfield 

Rifle,  Caliber  .45  ......................  32mo,  paper,  10 

*  Phelps's  Practical  Marine  Surveying  .....................  8vo,  2  50 

Powell's  Army  Officer's  Examiner  ......................  12mo,  4  00 

Sharpe's  Subsisting  Armies  ...................  32mo,  morocco,  1  50 

Wheeler's  Siege  Operations  ..............................  8vo,  2  00 

Wiuthrop's  Abridgment  of  Military  Law  ................  12mo,  2  50 

Woodhull's  Notes  on  Military  Hygiene  ..................  16mo,  1  50 

Young's  Simple  Elements  of  Navigation  ......  16mo,  morocco,  2  00 

"       ''     "'•  first          ' 


ASSAYING. 

SMELTING  —  OKE  DRESSING—  ALLOYS,  ETC. 

Fletcher's  Quant.  Assaying  with  the  Blowpipe..  16mo,  morocco,  1  50 

Furman's  Practical  Assaying  .............................  8vo,  3  00 

Earnhardt's  Ore  Dressing  .................................  8vo,  1  50 

O'Driscoll's  Treatment  of  Gold  Ores  ......................  8vo,  2  00 

Ricketts  and  Miller's  Notes  on  Assaying  ..................  8vo,  3  00 

Thurstou's  Alloys,  Brasses,  and  Bronzes  .................  8vo,  2  50 

Wilson's  Cyanide  Processes  ............................  12mo,  1  50 

The  Chloriuation  Process  .....................  .12uio,  150 

ASTRONOMY. 

PRACTICAL,  THEORETICAL,  AND  DESCRIPTIVE. 

Craig's  Azimuth  .........................................  4to,  3  50 

Doolittle's  Practical  Astronomy  ..........................  8vo,  4  00 

Gore's  Elements  of  Geodesy  ..............................  8vo,  2  50 

Hay  ford's  Text-book  of  Geodetic  Astronomy  .............  8vo.  3  00 

*  Michie  and  Harlow's  Practical  Astronomy  ...............  8vo,  3  00 

*  White's  Theoretical  and  Descriptive  Astronomy  ........  12mo,  2  00 

3 


BOTANY. 

GARDENING  FOR  LADIES,  ETC. 

Baldwin's  Orchids  of  New  England Small  8vo,  $1  50 

Thome's  Structural  Botany 16mo,  2  25 

Westermaier's  General  Botany.     (Schneider.)?.1?.'.  .\°/. 8vo,  2  00 

00  *•       ,o                                                                           >.'iioinafS'  "  -  ^'  * 

BRIDGES,  ROOFS,   Etc. 

CANTILEVER— DRAW — HIGHWAY — SUSPENSION. 

(See  also  ENGINEERING,  p.  7.) 

Boiler's  Highway  Bridges .v..7?£fl*:V 8vo,  2  00 

*  "       The  Thames  River  Bridge. .  .  . . 4to,  paper,  5  00 

Burr's  Stresses  in  Bridges . .1  AT-i?*ft(. . . .  .8vo,  3  50 

Crehore's  Mechanics  of  the  Girder 8vo,  5  00 

Dredge's  Thames  Bridges . : 7  parts,  per  part,  1  25 

J)u  Bois's  Stresses  in  Framed  Structures Small  4to,  10  00 

Foster's  Wooden  Trestle  Bridges 4to,  5  00 

Greene's  Arches  in  Wood,  etc 8vo,  2  50 

Bridge  Trusses 8vo,  2  56 

Roof  Trusses 8vo,  125 

Howe's  Treatise  on  Arches 8vo,  4  00 

Johnson's  Modern  Framed  Structures Small  4to,  10  00 

jjterriman  &  Jacoby's  Text-book  of  Roofs  and  Bridges. 

Part  I.,  Stresses .8vo,  250 

jyterriman  &  Jacoby's  Text-book  of  Roofs  and  Bridges. 

Part  II.,  Graphic  Statics. 8vo,  2  50 

Merriman  &  Jacoby's  Text-book  of  Roofs  and  Bridges. 

Part  III.,  Bridge  Design Svo,  2  50 

Merriman  &  Jacoby's  Text- book  of  Roofs  and  Bridges. 

Part  IV.,  Continuous,  Draw,  Cantilever,  Suspension,  and 

Arched  Bridges 8vo,  2  50 

*  Morison's  The  Memphis  Bridge Oblong  4to,  10  00 

WaddelPs  Iron  Highway  Bridges Svo,  4  00 

De  Pontibus  (a  Pocket-book  for  Bridge  Engineers). 

16mo,  morocco,  3  00 

"        Specifications  for  Steel  Bridges (In  press.) 

Wood's  Construction  of  Bridges  and  Roofs Svo,  2  00 

Wright's  Designing  of  Draw  Spans.     Parts  I.  and  II.. Svo,  each  2  50 

"              "          "      "        "         Complete Svo,  350 

4 


CHEMISTRY— BIOLOGY-PHARMACY— SANITARY  SCIENCE. 

QUALITATIVE — QUANTITATIVE— ORGANIC — INORGANIC,  ETC. 

Adriance's  Laboratory  Calculations 12mo,     $1  25 

Allen's  Tables  for  Iron  Analysis 8vo,  3  00 

Austeu's  Notes  for  Chemical  Students 12mo,  1  50 

Bolton's  Student's  Guide  in  Quantitative  Analysis 8vo,  1  50 

Boltwood's  Elementary  Electro  Chemistry (In  the  press.) 

Classen's  Analysis  by  Electrolysis.  (HerrickaudBoltwood.).8vo,  3  00 

Cohu's  Indicators  and  Test-papers 12mo  2  00 

Crafts's  Qualitative  Analysis.     (Schaeffer. ) 12mo,  1  50 

Davenport's  Statistical  Methods  with  Special  Reference  to  Bio- 
logical Variations 12mo,  morocco,  1  25 

Drechsel's  Chemical  Reactions.    (Merrill.) 12mo,  1  25 

Erdmann's  Introduction  to  Chemical  Preparations.     (Dunlap.) 

12mo,  1  25 

Fresenius's  Quantitative  Chemical  Analysis.    (Allen.) 8vo,  6  00 

Qualitative          "              "            (Johnson.) 8vo,  300 

v/y  (Wells.)         Trans. 

16th  German  Edition 8vo,  5  00 

Fuertes's  Water  and  Public  Health 12mo,  1  50 

Gill's  Gas  and  Fuel  Analysis 12mo,  1  25 

Hammarsten's  Physiological  Chemistry.   (Maudel.) 8vo,  4  00 

Helm's  Principles  of  Mathematical  Chemistry.    (Morgan ).12nio,  1  50 

Hopkins'  Oil-Chemist's  Hand-book 8vo,  3  00 

Ladd's  Quantitative  Chemical  Analysis 12rno,  1  00 

Landauer's  Spectrum  Analysis.     (Tingle.) 8vo,  3  00 

L5b's  Electrolysis  and  Electrosynthesis  of  Organic  Compounds1. 

(Lorenz.) 12rno,  100 

Mendel's  Bio-chemical  Laboratory 12mo,  1  50 

Mason's  Water-supply 8vo,  5  00 

v*      Examination  of  Water 12mo,  1  25 

Meyer's  Radicles  in  Carbon  Compounds.  (Tingle.) 12mo,  1  00 

Mixter's  Elementary  Text-book  of  Chemistry 12mo,  1  50 

Morgan's  The  Theory  of  Solutions  and  its  Results 12rno,  1  00 

Elements  of  Physical  Chemistry 12mo,  2  00 

Nichols's  Water-supply  (Chemical  and  Sanitary) 8vo,  2  50 

O'Brine's  Laboratory  Guide  to  Chemical  Analysis 8vo,  2  00 

Pinner's  Organic  Chemistry.     (Austen.) 12mo,  1  50 

Poole's  Calorific  Power  of  Fuels 8vo,  3  00 

Richards's  Cost  of  Living  as  Modified  by  Sanitary  Science..  12mo.  1  00 

and  Woodman's  Air,  Water,  and  Food 8vo,  2  00 

Ricketts   and   Russell's  Notes   on   Inorganic  Chemistry  (Non- 
metallic)  ,  Oblong  8vo,  morocco,  75 

Rideal's  Sewage  and  the  Bacterial  Purification  of  Sewage... 8vo,  3  50 

5 


Ruddiman's  Incompatibilities  in  Prescriptions 8vo,  $2  00 

Schimpf  s  Volumetric  Analysis ,J2mo,  2  50 

Spencer's  Sugar  Manufacturer's  Handbook 16mo,  morocco,  2  00 

Handbook    for    Chemists    of  Beet    Sugar    Houses. 

16mo,  rnorocco,  3  00 

Stockbridge's  Rocks  and  Soils. 8vo,  2  50 

*  Till  man's  Descriptive  General  Chemistry 8vo,  3  00 

Van  Deventer's  Physical  Chemistry  for  Beginners.    (Boltwood.) 

12nio,  1  50 

Wells's  Inorganic  Qualitative  Analysis 12mo,  1  50 

"      Laboratory   Guide   in   Qualitative  Chemical  Analysis. 

8vo,  1  50 

Whipple's  Microscopy  of  Drinking-water 8vo,  3  50 

Wiech inann's  Chemical  Lecture  Notes 12mo,  3  «00 

Sugar  Analysis .Small  8vo,  250 

Wulling's  Inorganic  Phar.  and  Med.  Chemistry 12mo,  2  00 


DRAWING. 

ELEMENTARY— GEOMETRICAL— MECHANICAL— TOPOGRAPHICAL. 

Hill's  Shades  and  Shadows  and  Perspective 8vo,  2  00 

MacCord's  Descriptive  Geometry 8vo,  3  00 

"          Kinematics 8vo,  500 

' '          Mechanical  Drawing 8vo,  4  00 

Mahan's  Industrial  Drawing.    (Thompson.') 2  vols.,  8vo,  3  50 

Reed's  Topographical  Drawing.     (H.  A.) 4to,  5  00 

Reid's  A  Course  in  Mechanical  Drawing 8vo.  2  00 

"      Mechanical  Drawing  and  Elementary  Machine   Design. 

8vo,  3  00 

Smith's  Topographical  Drawing.     (Macmillan.) 8vo,  2  50 

Warren's  Descriptive  Geometry 2  vols.,  8vo,  3  50 

"        Drafting  Instruments 12mo,  1  25 

Free-hand  Drawing 12nio,  1  00 

"        Linear  Perspective 12mo,  1  00 

"        Machine  Construction 2  vols.,  8vo,  7  50 

"        Plane  Problems 12mo,  1  25 

"        Primary  Geometry 12mo,  75- 

Problems  and  Theorems 8vo,  250 

"        Projection  Drawing 12mo,  150 

Shades  and  Shadows 8vo,  300 

"        Stereotomy— Stone-cutting , ...8vo,  250 

Whelpley's  Letter  Engraving 12mo,  2  00^ 

Wilson's  Free-hand  Perspective (In  press.) 

6 


ELECTRICITY  AND  MAQNETISM. 

ILLUMINATION— BATTERIES— PHYSICS— RAILWAYS. 

Anthony  and  Brackctt's  Text-book  of  Physics.     (Magi&.)   Small 

8vo,  $3  00 

Anthony's  Theory  of  Electrical  Measurements 12mo,  1  00 

Barker's  Deep- sea  .Soundings 8vo,  2  00 

Benjamin's  Voltaic  Cell 8vo,  3  00 

History  of  Electricity 8vo,  300 

Classen's  Analysis  by  Electrolysis.   (Hen  ick  and  Boltwood,)  8vo,  3  00 
Crehore  and  Squier's  Experiments  with  a  New  Polarizing  Photo- 
Chronograph 8vo,  3  00 

Dawson's  Electric  Railways  and  Tramways.     Small,  4to,  half 

morocco,  12  50 

*  "Engineering"  and  Electric  Traction  Pocket-book.      16mo, 

morocco,  5  00 

*  Dredge's  Electric  Illuminations. . .  .2  vols.,  4to,  half  morocco,  25  00 

'w;SuV             "             Vol.11 4to,  750 

Gilbert's  De  magnete.    (Mottelay .) 8vo,  2  50 

Holmau's  Precision  of  Measurements 8vo,  2  00 

"         Telescope-mirror-scale  Method Large  8vo,  75 

Lob's  Electrolysis  and  Electrosyuthesis  of  Organic  Compounds. 

(Lorenz.) ,...12mo,  1  00 

*Micliie's  Wave  Molion  Relating  to  Sound  and  Light 8vo,  4  00 

Morgan's  The  Theory  of  Solutions  and  its  Results 12mo,  1  00 

Niaudet's  Electric  Batteries      (Fishback.) .12mo,  2  50 

Pratt  and  Alden's  Street-railway  Road-beds 8vo,  2  00 

Reagan's  Steam  and  Electric  Locomotives 12rao,  2  00 

Tlmrstoii's  Stationary  Steam  Engines  for  Electric  Lighting  Pur- 
poses    8vo,  2  50 

*Tillman's  Heat , 8vo,  1  50 

Tory  &  Pitcher's  Laboratory  Physics (In  press) 

ENGINEERING, 

CIVIL — MECHANICAL — SANITARY,  ETC. 

(See  also  BRIDGES,  p.  4 ;  HYDRAULICS,  p.  9 ;  MATERIALS  OF  EN- 
GINEERING, p.  10 ;  MECHANICS  AND  MACHINERY,  p.  12  ;  STEAM 
ENGINES  AND  BOILERS,  p.  14.) 

Baker's  Masonry  Construction ,,.,,..  -8vo,  5  00 

"        Surveying  Instruments 12mo,  300 

Black's  U.  S.  Public  Works Oblong  4to,  5  00 

Brooks's  Street-railway  Location , 16mo,  morocco,  1  50 

Butts's  Civil  Engineers'  Field  Book 16mo,  morocco,  2  50 

Byrne's  Highway  Construction 8vo,  5  00 

7 


Byrne's  Inspection  of  Materials  and  Workmanship 16mo,  $3  00 

Carpenter's  Experimental  Engineering  8vo,  6  00 

Church's  Mechanics  of  Engineering — Solids  and  Fluids 8vo,  6  00 

Notes  and  Examples  in  Mechanics 8vo,  2  00 

Crandall's  Earthwork  Tables 8vo,  1  50 

' '          The  Transition  Curve 16mo,  morocco,  1  50 

*  Dredge's    Penn.    Railroad     Construction,    etc.      Large     4to, 

half- morocco,  $10;  paper,  5  00 

*  Drinker's  Tunnelling 4to,  half  morocco,  25  00 

Eissler's  Explosives — Nitroglycerine  and  Dynamite 8vo,  4  00 

Frizell's  Water  Power (In  press.} 

Folwell's  Sewerage 8 vo,  3  00 

Water-supply  Engineering . .  .8vo,  4  00 

Fowler's  Coffer-dam  Process  for  Piers .8vo.  2  50 

Gerhard's  Sanitary  House  Inspection 12mo,  1  00 

Godwin's  Railroad  Engineer's  Field-book 16mo,  morocco,  2  50 

Gore's  Elements  of  Geodesy 8vo,  2  50 

Howard's  Transition  Curve  Field-book 16mo,  morocco,  1  50 

Howe's  Retaining  Walls  (New  Edition.) 12mo,  1  25 

Hudson's  Excavation  Tables.     Vol.  II 8vo,  1  00 

Button's  Mechanical  Engineering  of  Power  Plants 8vo,  5  00 

"         Heat  and  Heat  Engines 8vo,  5  00 

Johnson's  Materials  of  Construction Large  8vo,  6  00 

"         Theory  and  Practice  of  Surveying Small  8vo,  4  00 

Kent's  Mechanical  Engineer's  Pocket-book 16mo,  morocco,  5  00 

Kiersted's  Sewage  Disposal 12mo,  1  25 

Mahan's  Civil  Engineering.      (Wood.) 8vo,  5  00 

Merriman  and  Brook's  Handbook  for  Surveyors.  .  .  .16ino,  mor.,  2  00 

Merriman's  Precise  Surveying  and  Geodesy 8vo,  2  50 

"          Sanitary  Engineering 8vo,  2  00 

Nagle's  Manual  for  Railroad  Engineers .16mo,  morocco,  3  00 

Ogdeu's  Sewer  Design < , . .  12mo,  2  00 

Pattou's  Civil  Engineering «8vo,  half  morocco,  7  50 

Patton's  Foundations ., 8vo,  5  00 

Philbrick's  Field  Manual  for  Engineers (In  press.) 

Pratt  and  Aldeu's  Street-railway  Road-beds 8vo,  2  00 

Rockwell's  Roads  and  Pavements  in  France 12mo,  1  25 

Schuyler's  Reservoirs  for  Irrigation Large  8vo.     (In  press.) 

Searles's  Field  Engineering , 16mo,  morocco,  3  00 

Railroad  Spiral 16mo,  morocco,  1  50 

Siebert  and  Biggin's  Modern  Stone  Cutting  and  Masonry. .  .8vo,  1  50 

:Smart's  Engineering  Laboratory  Practice 12mo,  2  50 

•Smith's  Wire  Manufacture  and  Uses Small  4to,  3  00 

Spalding's  Roads  and  Pavements 12mo,  2  00 

Hydraulic  Cement 12mo,  200 

8 


Taylor's  Prisuioidal  Formulas  uud  Earthwork; :.jid&  iU>i. . .  .8vo,  $1  50 

Thurston's  Materials  of  Construction  8vo,  5  00 

Tillson's  Street  Pavements  and  Paving  Materials.. 8vo.  (In  press.) 

*  Trautwine's  Civil  Engineer's  Pocket-book. . .  ,16mo,  morocco,  5  00 

*  ' '           Cross-section Sheet,  25 

*  ' '           Excavations  and  Embankments Svo,  2  00 

"            Laying  Out  Curves 12mo,  morocco,  2  50 

Waddell's  De  Pontibus  (A  Pocket-book  for  Bridge  Engineers). 

16mo,  morocco,  3  00 

Wait's  Engineering  and  Architectural  Jurisprudence Svo,  6  00 

Sheep,  6  50 

V      Law  of  Field  Operation  in  Engineering,  etc. .  .(In  press.) 

Warren's  Stereotomy— Stone-cutting Svo,  2  50 

Webb's  Engineering  Instruments.  New  Edition.  16mo,  morocco,  1  25 

"       Railroad  Construction Svo,  4  00 

Wegmann's  Construction  of  Masonry  Dams 4to,  5  00 

Wellington's  Location  of  Railways. Small  Svo,  5  00 

Wheeler's  Civil  Engineering Svo,  4  00 

Wilson's  Topographical  Surveying Svo,  3  50 

Wolff's  Windmill  as  a  Prime  Mover Svo,  3  00 

06.  t       .'uiiSt 'nuJ'WhiarK  !.•>:.'!  >'•!?  luui  LnffooW  &\mou;.'»;')3 

HYDRAULICS. 

WATER-WHEELS — WINDMILLS — SERVICE  PIPE — DRAINAGE,  ETC. 
{See  also  ENGINEERING,  p.  7.) 

Bazin's  Experiments  upon  the  Contraction  of  the  Liquid  Vein. 

(Trautwine. ) '.'.' . ; . . .'. Svo,  2  00 

Bovey 's  Treatise  on  Hydraulics. . . , i Svo,  4  00 

Coffin's  Graphical  Solution  of  Hydraulic  Problems. ......  12mo,  2  50 

Ferrel's  Treatise  on  the  Winds,  Cyclones,  and  Tornadoes. .  .bvo,  4  00 

Fol well's  Water  Supply  Engineering Svo,  4  00 

Fuertes's  Water  and  Public  Health 12mo,  1  50 

Ganguillet  &  Kutter's  Flow  of  Water.     (Bering  &  Trautwine.) 

Svo,  4  00 

Hazen's  Filtration  of  Public  Water  Supply Svo,  3  00 

Herschel's  115  Experiments : Svo,  2  00 

Kiersted's  Sewage  Disposal 12mo,  1  25 

Mason's  Water  Supply Svo,  5  00 

"     Examination  of  Water 12mo,  1  25 

Merriman's  Treatise  on  Hydraulics.. . . Svo,  4  00 

Nichols's  Water  Supply  (Chemical  and  Sanitary) Svo,  2  50 

Turneaure  and  Russell's  Water-supply (In  press.) 

Wegmaun's  Water  Supply  of  the  City  of  New  York 4to,  10  00 

Weisbach's  Hydraulics.     (Du  Bois.) ' Svo,  5  00 

Whipple's  Microscopy  of  Drinking  Water Svo,  3  50 

9 


Wilson's  Irrigation  Engineering 8vo,  $4  00 

"        Hydraulic  and  Placer  Mining 12mo,  2  00 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  00 

Wood's  Theory  of  Turbines Svo,  2  50 

LAW. 

ARCHITECTURE — ENGINEERING — MILITARY. 

Davis's  Elements  of  Law Svo,  2  50 

' '      Treatise  on  Military  Law Svo,  7  00 

Sheep,  7  50 

Murray's  A  Manual  for  Courts-martial 16mo,  morocco,  1  50 

Wait's  Engineering  and  Architectural  Jurisprudence Svo,  6  00 

Sheep,  6  50 

"      Laws  of  Field  Operation  in  Engineering (In  press.} 

Winthrop's  Abridgment  of  Military  Law 12mo,  2  50 

MANUFACTURES. 

BOILERS— EXPLOSIVES— IRON — STEEL— SUGAR — WOOLLENS,  ETC. 

Allen 's  Tables  for  Iron  Analysis Svo,  3  00 

Beaumont's  Woollen  and  Worsted  Manufacture 12ino,  1  50 

Bolland's  Encyclopaedia  of  Founding  Terms 12mo,  3  00 

The  Iron  Founder 12mo,  250 

Supplement 12mo,  250 

Bouvier's  Handbook  on  Oil  Painting 12mo,  2  00 

Eissler's  Explosives,  Nitroglycerine  and  Dynamite Svo,  4  00 

Ford's  Boiler  Making  for  Boiler  Makers ISino,  1  00 

Metcalfe's  Cost  of  Manufactures Svo,  5  00 

Melcalf 's  Steel— A  Manual  for  Steel  Users 12mo,  2  00 

*  Reisig's  Guide  to  Piece  Dyeing Svo,  25  00 

Spencer's  Sugar  Manufacturer's  Handbook  . .  .  .16mo,  morocco,  2  00 
"        Handbook    for    Chemists    of    Beet    Sugar    Houses. 

16mo,  morocco,  3  00 

Thurston's  Manual  of  Steam  Boilers. Svo,  5  00 

Walke's  Lectures  on  Explosives Svo,  4  00 

West's  American  Foundry  Practice 12mo,  2  50 

"      Moulder's  Text-book 12mo,  250 

Wiechmann's  Sugar  Analysis - Small  Svo,  2  50 

Woodbury's  Fire  Protection  of  Mills. Svo,  2  50  / 

MATERIALS  OF  ENGINEERING 

STRENGTH — ELASTICITY — RESISTANCE,  ETC. 
(See  also  ENGINEERING,  p.  7.) 

Baker's  Masonry  Construction Svo,  5  00 

Beardslee  and  Kent's  Strength  of  Wrought  Iron. Svo,  1  50 

10 


Bovey's  Strength  of  Materials. .  yiV?lfl.Y.wKtTl3$i< 8vo,  7  50 

Burr's  Elasticity  and  Resistance  of  Materials Svo,  $5  00 

Byrne's  Highway  Construction Svo,  5  00 

Church's  Mechanics  of  Engineering — Solids  and  Fluids 8vo,  6  00 

Du  Bois's  Stresses  in  Framed  Structures Small  4to,  10  00 

Johnson's  Materials  of  Construction 8vo,  6  00 

Lanza's  Applied  Mechanics.    8vo,  7  50 

Marlens's  Testing  Materials.     (Henning. ) 2  vols.,  Svo,  7  50 

Merrill's  Stones  for  Building  and  Decoration Svo,  5  00 

Merriman's  Mechanics  of  Materials 8vo,  4  00 

Strength  of  Materials 12mo,  1  00 

Pattou's  Treatise  on  Foundations Svo,  5  00 

Rockwell's  Roads  and  Pavements  in  France 12mo,  1  25 

Spaldiug's  Roads  and  Pavements 12mo,  2  00 

Thurston's  Materials  of  Construction Svo,  5  00 

Materials  of  Engineering 3  vols.,  8vo,  8  00 

Vol.  I.,  Non -metallic  . .  „. .  ..'iv' Svo,  2  00 

Vol.  II.,  Iron  and  Steel Svo,  3  50 

Vol.  III.,  Alloys,  Brasses,  and  Bronzes Svo,  2  50 

Wood's  Resistance  of  Materials 8vo,  2  00 

MATHEMATICS. 

CALCULUS— GEOMETRY — TRIGONOMETRY,  ETC. 


50 


Baker's  Elliptic  Functions -V* '•'•.', '.'£ '.'.  ^'."..".'l  .8vo,  1 

*Bass's  Differential  Calculus '....  v;.l ...... .12mo,  4  00 

Briggs's  Plane  Analytical  Geometry. . .  ..V; ..'. . ,...'.!'. 12mo,  1  00 

Chapman's  Theory  of  Equations ......  1  \. '.'.''. ..  .12mo,  1  50 

Compton's  Logarithmic  Computations .••'••• 12mo,  1  50 

Davis's  Introduction  to  the  Logic  of  Algebra. Svo,  1  50 

Halsted's  Elements  of  Geometry ..*?!;. W. Svo,  1  75 

"       Synthetic  Geometry Svo,  1  50 

Johnson's  Curve  Tracing ..I'.' 12mo,  1  00 

Differential  Equations— Ordinary  and  Partial. 

Small  Svo,  3  50 

"        Integral  Calculus 12mo,  1  50 

"        Unabridged.    Small  Svo.    (In  press.) 

"        Least  Squares 12mo,  150 

*Ludlow's  Logarithmic  and  Other  Tables.     (Bass.) Svo,  2  00 

*       "        Trigonometry  with  Tables.     (Bass.) Svo,  300 

*Mahan's  Descriptive  Geometry  (Stone  Cutting)  Svo,  1  50 

Merrimau  and  "Woodward's  Higher  Mathematics Svo,  5  00 

Merriman's  Method  of  Least  Squares Svo,  2  00 

Rice  and  Johnson's  Differential  and  Integral  Calculus, 

2  vols.  in  1,  small  8vo,  2  50 
11 


Rice  and  Johnson's  Differential  Calculus Small  8vo,  $3  00 

"  Abridgment  of  Differential  Calculus. 

Small  8vo,  1  50 

Totteu's  Metrology *V<~ 2j«w*«WHh»«a- > 8vo»  %  50 

"Warren's  Descriptive  Geometry. .  .>,wn^.^SHW,'i{.  .2  vols.,  8vo,  3  50 

I  $"        Drafting  Instruments 4  towtfcw 12mo,  1  25 

"        Free-hand  Drawing 12mo,  1  00 

"        Linear  Perspective 12mo,  100 

"        Primary  Geometry 12mo,  75 

)  t"        Plane  Problems ^Kma**  -ISmo,  1  25 

"        Problems  and  Theorems 8vo,  2  50 

' '        Projection  Drawing 12mo,  1  50 

Wood's  Co-ordinate  Geometry w  -8vo,  2  00 

0  £      Trigonometry.. 12mo,  1  00 

Woolf's  Descriptive  Geometry Large  8vo,  3  00 

MECHANICS-MACHINERY. 

TEXT-BOOKS  AND  PRACTICAL  WORKS. 
(See  also  ENGINEERING,  p.  8.) 

Baldwin's  Steam  Heating  for  Buildings 12mo,  2  50 

Barr's  Kinematics  of  Machinery 8vo,  2  50 

Benjamin's  Wrinkles  and  Recipes 12mo,  2  00 

Chordal's  Letters  to  Mechanics 12mo,  2  00 

Church's  Mechanics  of  Engineering 8vo,  6  00 

Notes  and  Examples  in  Mechanics 8vo,  2  00 

Crehore's  Mechanics  of  the  Girder 8vo,  5  00 

Cromwell's  Belts  and  Pulleys 12mo,  1  50 

Toothed  Gearing 12mo,  1  50 

Compton's  First  Lessons  in  Metal  Working 12mo,  1  50 

Compton  and  De  Groodt's  Speed  Lathe 12mo,  1  50 

Dana's  Elementary  Mechanics 12rno,  1  50 

Dingey's  Machinery  Pattern  Making 12mo,  2  00 

*  Dredge's    Trans.     Exhibits    Building,     World     Exposition. 

Large  4to,  half  morocco,  5  00 

Du  Bois's  Mechanics.     Vol.  I.,  Kinematics 8vo,  3  50 

Vol.  II.,  Statics 8vo,  400 

Yol.  III.,  Kinetics 8vo,  350 

Fitzgerald's  Boston  Machinist 18mo,  1  00 

Flather's  Dynamometers 12mo,  2  00 

Rope  Driving 12mo,  200 

Hall's  Car  Lubrication 12mo,  1  00 

Holly's  Saw  Filing 18mo,  75 

Johnson's  Theoretical  Mechanics.      An  Elementary  Treatise. 
(In  the  press.) 

Jones's  Machine  Design.     Part  I.,  Kinematics 8vo,  1  50 

12 


Jones's  Machine  Design.     Part  II.,  Strength  and  Proportion  of 

Machine  Parts. .'.  ...:.'"  %'j^'y -".'.'•  •  «,.  •  .,-..t 8vo,     $3  00 

Lanza's  Applied  Mechanics •/••*>•  f  •"•  •  •  •-.<•  •  •  •  y  ••  •  •  -8vo,  7  50 

MacCord's  Kinematics .'.'... .' ;.*.'.  .'.'.V.'  l..^?. ... . .  .8vo,  5  00 

Merriman's  Mechanics  of  Materials,  ,\ .. . :.  .-,'.1,1'.'.,.".  1 8vo,  4  00 

Metcalfe's  Cost  of  Manufactures .". '.'. .'.  .v  » .'.'.''.' . . 8vo,  5  00 

*Michie's  Analytical  Mechanics ' 8vo,  4  00 

Richards's  Compressed  Air. . . . /.'"'.,. . . !'. 12mo,  1  50 

Eobinson's  Principles  of  Mechanism 8vo,  3  00 

Smith's  Press-working  of  Metals 8vo,  3  00 

Thurston's  Friction  and  Lost  Work 8vo,  3  00 

The  Animal  as  a  Machine 12mo,  100 

Warren's  Machine  Construction 2  vols.,  8vo,  7  50 

Weisbach's  Hydraulics  and  Hydraulic  Motors.    (Du  Bois.)..8vo,  5  00 
"          Mechanics    of   Engineering.      Vol.    III.,    Part  I., 

Sec.  I.     (Klein.)....... 8vo,  500 

Weisbach's  Mechanics    of  Engineering.     Vol.   III.,    Part  I., 

Sec.  II.     (Klein.) '. '.  '. .,.'.'.;..'.  v 8vo,  5  00 

Weisbach's  Steam  Engines.     (Du  Bois.) '.','  1^.,^ . 8vo,  5  00 

Wood's  Analytical  Mechanics :. . .  ^.'l'.'.!.".. . .  .8vo,  3  00 

"      Elementary  Mechanics M,.... 12mo,  1  25 

*';  «            " •••:••             "           Supplement  and  Key 12mo,  1  25 

Uw  1*        «*^^ »....'.-«..- 

METALLURGY. 

IRON— GOLD— SILVER — ALLOYS,  ETC. 

Allen's  Tables  for  Iron  Analysis 8vo,  3  00 

Egleston's  Gold  and  Mercury Large  8vo,  7  50 

Metallurgy  of  Silver Large  8vo,  7  50 

*  Kerl's  Metallurgy — Copper  and  Iron 8vo,  15  00 

*  "           "               Steel,  Fuel,  etc 8vo,  1500 

Kunhardt's  Ore  Dressing  in  Europe 8vo,  1  50 

Metcalf's  Steel— A  Manual  for  Steel  Users 12mo,  2  00 

O'Driscoll's  Treatment  of  Gold  Ores 8vo,  2  00 

Thurston's  Iron  and  Steel 8vo,  3  50 

"          Alloys 8vo,  250 

Wilson's  Cyanide  Processes , 12mo,  1  50 

MINERALOGY   AND  MINING. 

MINE  ACCIDENTS — VENTILATION— ORE  DRESSING,  ETC. 

Barriuger's  Minerals  of  Commercial  Value Oblong  morocco,  2  50 

Beard's  Ventilation  of  Mines 12mo,  2  50 

Boyd's  Resources  of  South  Western  Virginia 8vo,  3  00 

Map  of  South  Western  Virginia Pocket-book  form,  2  00 

Brush  and  Penfield's  Determinative  Mineralogy.   New  Ed.  8vo,  4  00 

13 


Chester's  Catalogue  of  Minerals 8vo,  $1  25 

Paper,  50 

"       Dictionary  of  the  Names  of  Minerals 8vo,  3  00 

Dana's  American  Localities  of  Minerals Large  8vo,  1  00 

"      Descriptive  Mineralogy    (E.S.)  Large  8 vo.  half  morocco,  12  50 

"      First  Appendix  to  System  of  Mineralogy.    . .   Large  8vo,  1  00 

"      Mineralogy  and  Petrography.     (J.  D.) . . .  - 12mo,  2  00 

"      Minerals  and  How  to  Study  Them.     (E.  S.).. 12mo,  1  50 

"      Text-book  of  Mineralogy.    (E.  S.)..  .New  Edition.     8vo,  400 
*  Drinker's  Tunnelling,  Explosives,  Compounds,  and  Rock  Drills. 

4to,  lialf  morocco,  25  00 

Egleston's  Catalogue  of  Minerals  and  Synonyms 8vo,  2  50 

Eissler's  Explosives — Nitroglycerine  and  Dynamite 8vo,  4  00 

Hussak's  Rock-forming  Minerals.     (Smith.) Small  8vo,  2  00 

Ihlseng's  Manual  of  Mining 8vo,  4  00 

Kunhardt's  Ore  Dressing  in  Europe 8vo,  1  50 

O'Driscoll's  Treatment  of  Gold  Ores 8vo,  2  00 

*'  Peufield's  Record  of  Mineral  Tests Paper,  8vo,  50 

Roseubusch's    Microscopical    Physiography   of    Minerals    and 

Rocks.     (Iddings.).. 8vo,  500 

Sawyer's  Accidents  in  Mines Large  8vo,  7  00 

Stockbridge's  Rocks  and  Soils 8vo,  2  50 

Walke's  Lectures  on  Explosives 8vo,  4  00 

Williams's  Lithology 8vo,  3  00 

Wilson's  Mine  Ventilation 12mo,  1  25 

"        Hydraulic  and  Placer  Mining 12mo,  250 

STEAM  AND  ELECTRICAL  ENGINES,  BOILERS,  Etc. 

STATIONARY — MARINE— LOCOMOTIVE — GAS  ENGINES,  ETC. 
(See  also  ENGINEERING,  p.  7.) 

Baldwin's  Steam  Heating  for  Buildings 12mo,  2  50 

Clerk's  Gas  Engine..... !\ Small  8vo,  400 

Ford's  Boiler  Making  for  Boiler  Makers. 18mo,  1  00 

Hemenway's  Indicator  Practice 12mo,  2  00 

Kneass's  Practice  and  Theory  of  the  Injector 8vo,  1  50 

MacCord's  Slide  Yalve. '. 8vo,  2  00 

Meyer's  Modern  Locomotive  Construction 4to,  10  00 

Peabody  and  Miller's  Steam-boilers 8vo,  4  -00 

Peabody's  Tables  of  Saturated  Steam. 8vo,  1  00 

."          Thermodynamics  of  the  Steam  Engine 8vo,  5  00 

"         Yalve  Gears  for  the  Steam  Engine 8vo,  2  50 

"          Manual  of  the  Steam-engine  Indicator 12ino,  1  50 

Pray's  Twenty  Years  with  the  Indicator Large  8vo,  2  50 

Pupin  and  Osterberg's  Thermodynamics 12mo,  1  25 

14 


Reagan's  Steam  and  Electric  Locomotives *JtI3?J*.  .12mo,     $2  00 

Routgen's  Thermodynamics.     (Du  Bois. ) 8vo,  5  00 

Sinclair's  Locomotive  Running 12mo,  2  00 

Snow's  Steam-boiler  Practice 8vo.  3  00 

Thurston's  Boiler  Explosions 12mo,  1  50 

"           Eugine  and  Boiler  Trials .8vo,  500 

"  Manual  of  the  Steam  Engine.      P;irt  I.,   Structure 

and  Theory 8vo,  6  00 

"  Manual  of  the   Steam  Eugine.      Part  II.,    Design, 

Construction,  and  Operation 8vo,  6  00 

2  parts,     10  00 

Thurston's  Philosophy  of  the  Steam  Engine 12mo,  75 

"'          Reflection  on  the  Motive  Power  of  Heat.    (Carnot.) 

12mo,  1  50 

"           Stationary  Steam  Engines 8vo,  2  50 

"           Steam-boiler  Construction  and  Operation 8vo,  5  00 

Spangler's  Valve  Gears 8vo,  2  50 

Weisbach's  Steam  Engine.     (Du  Bois.) 8vo,  5  00 

Whitham's  Steam-engine  Design 8vo,  5  00 

Wilson's  Steam  Boilers.     (Flather.) 12mo,  2  50 

Wood's  Thermodynamics,  Heat  Motors,  etc 8vo,  4  00 

ftO    fl  O'V^I-l-'M!    'lil'.l    .iMj-    II;  ...,.(>•»;  !'JJJ*lT) 

TABLES,  WEIGHTS,  AND  MEASURES. 

FOR  ACTUARIES,  CHEMISTS,  ENGINEERS,  MECHANICS— METRIC 
TABLES,  ETC. 

,ru  i/.      -jf-iiH     ><--ncbII     fc-feivjJJ'jJ 

Adriance's  Laboratory  Calculations 12mo,  1  25 

Allen's  Tables  for  Iron  Analysis 8vo,  3  00 

Bixby's  Graphical  Computing  Tables Sheet,  25 

Compton's  Logarithms 12mo,  1  50 

Craudall's  Railway  and  Earthwork  Tables. . .  ..ltl,;.fI»,T^f .  .^y^^.  1  50 

Egleston's  Weights  and  Measures 18mo,  75/ 

Fisher's  Table  of  Cubic  Yards .Cardboard,  25 

Hudson's  Excavation  Tables.     Vol.  II 8vo,  1  00 

Johnson's  Stadia  and  Earthwork  Tables 8vo,  1  25 

Ludlow's  Logarithmic  and  Other  Tables.     (Bass.) 12mo,  2  00 

Totteu's  Metrology 8vo,  2  50 

VENTILATION. 

STEAM  HEATING— HOUSE  INSPECTION— MINE  VENTILATION. 

Baldwin's  Steam  Heating 12mo,  2  50 

Beard's  Ventilation  of  Mines 12mo,  2  50 

Carpenter's  Heating  and  Ventilating  of  Buildings 8vo,  3  00 

Gerhard's  Sanitary  House  Inspection 12mo,  1  00 

Wilson's  Mine  Ventilation 12mo,  1  25 

15 


MISCELLANEOUS  PUBLICATIONS. 

Alcott's  Gems,  Sentiment,  Language Gilt  edges,  $5  00 

Davis's  Elements  of  Law 8vo,  2  00 

Emmon's  Geological  Guide-book  of  the  Rocky  Mountains.  .8vo,  1  50 

Fen-el's  Treatise  on  the  Winds 8vo,  4  00 

Haines's  Addresses  Delivered  before  the  Am.  Ry.  Assn.  ..12mo,  2  50 

Mott's  The  Fallacy  of  the  Present  Theory  of  Sound.  .Sq.  lOmo,  1  00 

Richards's  Cost  of  Living 12rno,  1  00 

Ricketts's  History  of  Rensselaer  Polytechnic  Institute .8vo,  3  00 

Rotherhain's    The    New    Testament     Critically    Emphasized. 

12ino,  1  50 
"              The  Emphasized  New  Test.     A  new  translation. 

Large  8vo,  2  00 

Totteu's  An  Important  Question  in  Metrology 8vo,  2  50 

*  Wiley's  Yosemite,  Alaska,  and  Yellowstone 4to,  3  00 

•  H'll'' 

HEBREW  AND  CHALDEE  TEXT-BOOKS. 

FOR  SCHOOLS  AND  THEOLOGICAL  SEMINARIES. 

Gesenius's  Hebrew  and   Chaldee  Lexicon  to  Old  Testament. 

(Tregelles. ) Small  4to,  half  morocco,  5  00 

Green's  Elementary  Hebrew  Grammar 12mo,  1  25 

Grammar  of  the  Hebrew  Language  (New  Edition). 8 vo,  3  00 

Hebrew  Chrestomathy. 8vo,  2  00 

Letteris's    Hebrew  Bible  (Massoretic  Notes  in  English). 

8vo,  arabesque,  2  25 

MEDICAL. 

Hammarsten's  Physiological  Chemistry.   (Mandel.) 8vo,      4  00 

Mott's  Composition,  Digestibility,  and  Nutritive  Value  of  Food. 

Large  mounted  chart,       1  25 

Ruddiman's  Incompatibilities  in  Prescriptions 8vo,       2  00 

Steel's  Treatise  on  the  Diseases  of  the  Ox 8vo,       6  00 

Treatise  on  the  Diseases  of  the  Dog 8vo,       350 

Woodhull's  Military  Hygiene 16mo,      1  50 

Worcester's  Small  Hospitals — Establishment  and  Maintenance, 
including  Atkinson's  Suggestions  for  Hospital  Archi- 
tecture  12mo,  1  25 

16 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
iMPED  BELOW 


SEP    1  1923 

RPR  2418679* 

MAY  2  4 1967 


30m-6,'14 


YC  13293 


250. 


I  I 


.5 


